Is there a way to wirelessly transmit data (preferably a string but numbers will do) in between 2 Raspberry Pis? The data must be transmitted without use of bluetooth or internet and have a range of about 40 feet. It can use GPIO or USB or anything else. Also the smaller the better! The data would be GPS coordinates, time and some other numbers and strings. In my research I found this Raspberry Pi Forums post but I am not sure if it would work.
Any programming language (except Assembly), software or extra hardware is fine.