Oliver Yeh, Justin Lee, Eric Newton have put a camera into near space and took a ton of pictures for a cost of only $150. The most interesting thing is that unlike most of these balloon projects there was no custom electronics involved. Instead they used a GPS enabled cell phone to send them the GPS location data.

"We designed a low cost balloon-launch platform that did not require the use of expensive equipment such as radio modems (the total cost of our device did not exceed 150 dollars) or complicated hardware hacking (all of the components of our device were common electronics available off-the-shelf in stores). The GPS receiver was a Motorola i290 “Boost Mobile” prepaid phone with internet and GPS capability (set up with Accutracking to constantly report its GPS location)."