I have bought at least 4 different GPS/mag units from eBay.
- Get a Ublox GPS/mag.
- Be aware that next LP release is planned to have external I2C mag support
- Be aware that next LP release may have Sparky2 FC support, and Sparky2 has more sensor ports available than Revo (and way more than Nano).
- Be aware that we are seeing problems with the Neo8 GPS's. The GPS position can jump a fairly long way between two consecutive location packets. If you want something right now vs. being safe and waiting for further testing on this (and can solder some plugs on), I would get a Neo7 from eBay like this one. This looks like the Neo7 that I have that is my current top pick.
http://www.ebay.com/itm/CRIUS-NEO-GPS-MAG-V2-NEO-7M-GPS-Module-w-Compass-for-APM-Pixhawk-PX4-Flight-SN-/281814729403- If size matters, the Neo8 is smaller, and you can get even smaller GPS's than the Neo8, but my experience is the smaller, the lower performance (smaller antenna).
- There is some Ublox testing that shows that Neo8 with it's higher sat count does better in city "concrete canyons".
- are you going to stack it on an e.g. Revo or mount it on a pole? There is a Neo6 that can be modified a little to make it stackable.
- are you OK with soldering different ends on the GPS cable? If not, you can search around and find one for OpenPilot for maybe $10 more.
Here are some standard Flexi/Main connectors. 20 for $6 shipped. That's enough to last a while.
http://www.ebay.com/itm/251979895512Here is some tiny heat shrink tubing to help you make nice cables. 1M for $1 shipped.
http://www.ebay.com/itm/311263739481For reference, the Neo8 being discussed
http://www.ebay.com/itm/Ublox-NEO-M8N-Flight-Controller-GPS-with-Protective-Shell-for-PIX-PX4-Pixhawk-l-/301663028659