Another contender in the race for space is Radiotronix. I have been using their WI232FHSS-250 modules at 900 MHz with great success. The link software is a breeze to set up, and it does have factory default reset on power up if necessary. So far, I have gotten 2 miles LOS with little stubby antennas. You can transmit at up to 115K baud and the units can be configured for auto retransmit when no acknowledgement from the receiving unit. Just feed them serial, and get it at the receive end, right out of the box. I've been very happy with them.Available from Mouser.
Ron