This in fact is not new, various groups have had quite sophisticated online tracking for some time. Perhaps the best of the bunch is the UKHAS  balloon tracking program which you can find here:
It's open source (of course!) and is run on bits of software contributed by various groups. It integrates with the UKHAS 'distributed listener', where anyone with a suitable radio (most HAMs) can listen in to a balloon flight and automatically decode and upload telemetry to the online map. The sound card software is a fork of fldigi  which has been modified to do all the uploading, and is cross-platform.
The UKHAS tracker also makes use of some flight prediction software from the Cambridge University Spaceflight group  to give live real-time flight and landing predictions so anyone chasing the balloon knows where to drive.
All of this stuff is FOSS. It's a glorious little cul-de-sac of geeky openness. Happy days!