DIY Fitness Tracker

Building a Personal Fitness Tracker

May 11, 2024 - Willem L. Middelkoop

As a little side-project, squeezed between my normal work, I have been working on something of personal interest: a native workout tracking app for iOS. I wanted to make my smartwatch obsolete, instead using my phone to track workouts. How hard could it be to gather detailed sensor data using native Swift APIs?

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Screenshots of the app's onboarding process: asking for permissions and guiding new users

Nothing makes you feel alive like going outside for some physical action - I love working out!

Not your average debugging session: Fietselfstedentocht 2024

Different configurations of realtime data

Designing a paywall for my app: not my favourite ask from users, but it is a very important one nonetheless.

"Goin' the extra mile": 8 hours on my bike to test battery usage (note: there is still 23% power left!)

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Articles (156)

2025-01-18 Master of Change
2024-12-19 Data versus Feeling
2024-12-09 The Problem With Bitcoin
2024-11-11 Write your own words
2024-11-10 Go Viral on X
2024-10-20 Marathon
2024-09-10 I see dead people
2024-05-11 Developing a native iOS app
2024-03-24 Half Marathon
2024-03-05 No, I Won't Build That!
2024-02-16 Vision Pro
2024-01-16 Health and fitness data
2023-12-15 Backup Rotation Scheme
2023-11-10 Apple Watch as Phone
2023-11-01 And... there is light!
2023-10-14 Giving AI Training
2023-10-13 Hello, stranger
2023-08-23 The Same, Differently
2023-05-31 Impact of training
2023-05-08 Tablet as Tool
2023-05-03 Using AI to generate code
2023-05-01 Working Offline First
2023-04-20 Tips for Long-Distance Cycling
2023-04-05 Cutting Cloud Costs
2023-02-08 Back to the University
2022-12-22 Rolex DateJust 36
2022-11-01 Moving to the countryside
2022-10-23 MUSE in Carré
2022-09-15 The Ultimate Freedom Bike
2022-09-11 Computer says no
2022-07-30 CAPTCHA Alternative
2022-07-17 Offline Music
2022-04-18 Snake '97 High Scores
2022-01-14 Wearing WHOOP 4.0
2021-12-09 For the love of mini
2021-11-19 Escaping the flat tires
2021-10-25 Using Google Free Android
2021-09-30 Inspiration from a child
2021-08-31 Protecting VMware ESXi
2021-07-13 The birth of a child
2021-06-30 Migrating to the Cloud
2021-06-05 Wearing Grand Seiko
2021-05-31 Using the reMarkable paper tablet
2021-05-04 Hospitalised with MCADD
2021-04-15 Enter text without keys
2021-04-10 Fixed Gear Gran Fondo
2021-03-26 Art of visualisation
2021-03-25 Three tips to make a content strategy work
2021-02-28 Wearing two watches
2021-02-22 The value of notifications
2021-02-02 Realtime service uptime monitoring
2021-01-31 Building a product platform
2021-01-14 Abandoning my own tablet OS
2021-01-10 Commuter bike checkup
2020-12-31 Working with special hardware from China
2020-12-15 Why Apple Silicon is a big deal
2020-12-02 Designing a multi dimensional capacity queue
2020-11-30 Designing my own watch
2020-11-22 Replacing a Shimano shift cable
2020-11-03 The joy of a simple laptop
2020-10-31 Increase traffic to your blog with a RSS feed
2020-10-30 How to use rsync to make backups
2020-10-15 Rescuing photos from a crashed iMac
2020-09-29 Riding with Omata One
2020-09-28 Refining my tablet OS experience
2020-09-16 Syncing files seamlessly between smartphone and tablet
2020-08-31 Free from the iCloud: Escaping Apple Photos
2020-08-23 Cleaning a vintage watch
2020-08-11 The best keyboard for iPad
2020-07-31 Influencing purchase behaviour
2020-07-30 Upgrading a 27-inch iMac 5K to 14 terabytes
2020-07-09 Repairing a Giro AEON bicycle helmet
2020-06-24 Some thoughts on touch screen user interface design
2020-06-17 Tudor Black Bay 36 long-term review
2020-06-12 Linking Lemmid Store with kitchens
2020-05-25 Different ways to visualise health
2020-05-11 Scalable application design without magic
2020-05-01 Designing an interface for a food ordering page
2020-04-30 Minimalistic road bike with Gates carbon drive
2020-04-14 Talking tablets: what makes a great tablet?
2020-04-01 Traffic shaping using iptables and tc
2020-03-25 Designing and implementing a (micro) payment system
2020-03-09 Making my own tablet OS
2020-03-03 Monolithic vs Microservices software architecture
2020-02-28 Your own addressbook and calendar cloud
2020-02-13 The day I sold my car
2020-01-28 Measuring cholesterol levels in blood
2020-01-24 Improve your sleep by blocking light
2019-12-31 Whoop strap review: 24/7 wearable sensor
2019-12-01 Realtime human pose recognition through computer vision
2019-11-26 Supernova E3 Pro 2 dynamo powered headlight
2019-11-22 Building a professional 72TB NAS
2019-10-19 Flying in a C47-A (DC-3) classic plane
2019-10-07 Multi-Window support in your iPad app
2019-09-27 Visiting an international hackers conference
2019-09-10 Fighting backscatter spam at server level
2019-08-28 Riding with a power meter on your bike
2019-08-18 Creating a minimal road bike
2019-07-16 Limitations of sleep tracking using a wearable
2019-07-15 Optical vs chest strap heart rate monitors
2019-06-25 Assembling a cargo bike
2019-06-24 Six months with MCADD
2019-05-29 Solo around the Markermeer (211KM)
2019-05-24 Dig for dummies
2019-04-30 The best bike computer app: Cyclemeter
2019-04-25 Search like a pro: Google search operators
2019-03-31 WordPress: 10 tips to secure your website
2019-03-20 Servicing a robot vacuum cleaner
2019-02-28 Understanding the security concerns in shared hosting
2019-02-27 One year on the ultimate commuter bike
2019-01-29 Born with MCADD
2019-01-24 My first weeks as dad
2018-12-22 Business in a bag
2018-12-06 Do amazing things with a focused mind
2018-11-16 Around town in an electric car
2018-11-02 Is the Apple Watch the modern tool watch?
2018-10-16 Rescuing files from a broken harddisk
2018-10-09 Using a budget Android as main smartphone
2018-09-27 Swimming and cycling with Apple Watch
2018-09-26 Optimising images for the web and performance
2018-08-21 Space travelling from El Teide
2018-08-20 Google Analytics vs AWStats
2018-07-20 Helping people with free software
2018-07-10 Enjoy a festival without alcohol
2018-06-09 Removing paint from a bike frame
2018-06-02 Creating a minimal iPhone stand
2018-05-17 Listen to your body
2018-05-09 Lunch by plane
2018-04-30 Off the grid: Working on 100% renewable energy
2018-04-18 Outside the comfort zone: amateur acting
2018-03-10 Cyber security: 5 easy tips to protect your server against hackers
2018-03-07 Tablet as main computer
2018-02-24 Creating the ultimate commuter bike
2018-02-21 Updating Snake '97
2018-01-21 Something the smartwatch will never have: patina
2018-01-08 Lessons from a takeaway plastic bag
2017-12-02 Commuting by bike
2017-11-15 Collecting health data with Biostrap
2017-10-23 From tree to table
2017-09-14 Saving a MacBook Air with exploded battery
2017-09-02 Climbing Mount Etna
2017-08-31 Clouds below my floor
2017-07-31 The day I killed my LAN
2017-06-30 Fietselfstedentocht 2017
2017-05-31 Beast of the Green Hell
2017-04-30 Smartwatches vs Mechanical watches
2017-03-26 Repairing a Nintendo Gameboy Advance SP
2017-02-16 Programming on Apple Watch
2017-01-30 iPad Pro next to my primary machine
2016-12-31 One year of cycling
2016-11-21 Being a volunteer in Amsterdam-Zuidoost
2016-10-01 Harvesting boredom to let creativity flourish
2016-09-03 Batavus Champion bike from 1978
2016-08-15 iPad Pro as primary computer
2016-07-15 Cash is king, or is it?
2016-06-23 Building the blog... in style!