TracksoarByonics Micro-Trak RTGSainSonic AP510BigRedBee
tracksoar sizemt-30001_1_96IMG_3150
Size (without battery holder)2" long
3/4" wide
1/2" thick
3.5" long
1" wide
1/2" thick (estimated)
9" long
3.1" wide
1.1" thick
3.3" long
1.3" wide
1/2" thick (esitmated)
Weight (with batteries and holder)under 2 ounces (with battery holder and batteries)unknown100 grams without case136 grams w/ 5x AAs
Open SourceYesNoNoNo
Add additional sensorsYes
GPIO/I2C/SPI
NoNo
Sensors IncludedYes
Temperature
Pressure
Humidity
N/ATemperatureN/A
Frequencies144 MHz
120 - 180 mhz and 434 mhz (avilable with pin compatible transmitters)
144 - 148 MHzFrequency Agile (136 - 175 MHz)Frequency Agile (144 - 148 MHz) and 434 MHz
Transmit Power300mW10W1W1 - 5 W
power source1.2 - 5 volts
2 X AA lithium ion batteries
9 - 15 volts
9 volt lithium battery
rechargeable 3300 mah lithium battery5 x AA
Battery Life
(at 1 minute transmit interval)
12 hours at 32F
(based on 2 AA lithium batteries)
6 hours (estimated based on a lithium 9v battery)
24 Hours (at 1 minute transmit interval)48 hours (at 1 minute transmit interval)
Price$200$220$99$265
Websitetracksoar.combyonics.comhttp://www.sainsonic.com/bigredbee.com

here is an in depth review by an independent weather balloon enthusiast:

http://bear.sbszoo.com/construction/traker/Tracksoar/V1-1.htm