Three years ago I was googling about high altitude balloons and I ended up with pico (floater) balloon projects. I was really impressed with some amateur radio operators efforts to circumnavigate around the world with party balloons and track them.
Six months later I got my amateur radio license and started flights with heavy APRS trackers. Since payload is very heavy, balloons maximum altitude never exceeded 9.000 meters and modules I used was not frequency agile.
So we (TA2MUN and TA9OHC) decided to develop a lightweight, extendable, affordable and open source APRS tracker. Since our tracker is very light and frequency agile, it's very convenient for pico (floater) balloon and HAB (High Altitude Balloon) projects. LightAPRS Tracker has been developed for nearly two years now and has been proven on many flights.
You can check out our tracker using following links:
Github page : https://github.com/lightaprs/LightAPRS-1.0
Shop : http://www.qrp-labs.com/lightaprs.html
Please do not hesitate to share if you have questions or comments about our tracker