If you are going through walls, the Radiotronix Wi.232 transceivers are great. They transmit at 900 MHz, with about 20 mW of RF at the antenna The connection is RS232 at any baud rate up to 115Kbaud. With a little bud of an antenna, I was getting 800 feet. The new FHSS versions are more powerful, but more expensive. I am using the 1/4 watt modules for a 2 mile link up a mountain with a solar powered weather station. I figger 10 miles LOS on these gems!
Ron