While the world of fitness trackers is exploding in popularity there are a limited number of devices that offer developer access through APIs and SDKs. Getting access can mean real-time raw sensor data, saving your personal history or full on application developement. Currently health data formats and access differ quite a bit between tracking devices so direct access through APIs and SDKs can be a game changer for the skilled quantified selfer or health researcher. Below is a summary of commercial fitness trackers that offer APIs and SDKs.

• FitBit – One of most mature public Web APIs available. Fitbit made their API public in Feb. 2011. There are many cross platform client libraries which is necessary as FitBit dropped Apple Healthkit support. Check out their Docs and Forum.
• Garmin – Garmin offers their Connect IQ SDK which is based on Monkey C they claim it’s similar to Java, Ruby and Python. The SDK is available for Win/Mac and allows the user to make watch faces, widgets, apps and custom data fields. Looking through the Connect store there are quite a bit of user contributions and a lot more potential for custom 3rd party sensors to be logging data through Garmin hardware.
• Apple – Much like Garmin Apple does not make things easy. There is no Web API to query, but there is an SDK for iOS and HealthKit which provide a structured way to build apps and store the data for long term retrieval. Apple’s SDK for the watch is just like the phone so you will be coding in Swift or Objective-C.
• Jawbone – The Jawbone up offers both API and SDK access.
• Withings –  Withings has a simple Web API that works with many of thier higher end quantified self hardware. Withings offers several wrist based trackers, but they also have an extended line of health monitors in the form of scales, sleep monitoring alarm clocks, blood pressure cuffs and much more.
• Nike+ – Nike has a significant offering for developers in the forms of Web API, iOS SDK, Android SDK and JavaScript SDK. Nike is the first company on this list to allow raw hardware data.
• MisFit – Misfit offers an API, three different SDK’s and a scientific library. Since their range of features and
• Angel Sensor – Wristband that monitors vitals {heart rate, blood oxygen, skin temp, activity}. Angel Sensor provides an SDK and apps on GitHub. The SDK supports iOS and Android and the code is all there although last I checked not actually under an open source license. Angel is one of two companies here that allow access to the raw hardware data.