LightAPRS-W is and affordable, smallest, lightest, powerful and open source APRS tracker with WSPR. It makes tracking pico balloons simple and easy. It is able to report location, altitude, temperature and pressure to the internet ([APRS-IS](http://status.aprs2.net)) or direct to an amateur radio once a minute with a solar panel/super capacitors or just 4xAAA batteries. Because LightAPRS-W is open source you can add your own custom sensors via I2C/SPI pins.  

Key Features

• Ready-assembled PCB: all components are SMD and already soldered
• Open Source: Software is open. You can easily modify the source code. The source code is shared via GitHub 
• Arduino Compatible MCU: Since MCU is Arduino compatible, you can use Arduino IDE and libraries to program LightAPRS-W 2.0.
• Extendable: Using I2C and SPI pins you can add extra sensors ( and their libraries) to LightAPRS-W 2.0 and programme it as you wish.
• 100 mWatt Radio: 100 mWatt is optimum for airborne projects.
• 10 mWatt HF Radio: Si5351A clock generator, Si5351 Arduino library and Etherkit JTEncode library generates a set of channel symbols for WSPR based on the user providing a callsign, Maidenhead grid locator, and power output for WSPR.
• High Quality GPS: No need to comment :) Ublox is one of the best GPS manufacturers.
• Price: LightAPRS-W 2.0 is more affordable (140$) than any other APRS+WSPR tracker

Full details: http://qrp-labs.com/lightaprsw2