It's a lot more difficult than you'll expect if you're not into that kind of stuff. My friend Tiffany Yep does that sort of stuff a lot (mostly the software side, that is) and she finds it quite easy, but I have a hard time understanding it. In particular, it's a lot more difficult to receive and interpret the data than it is to encode and transmit it.
Depending on your requirements, I would suggest some cheap microcontrollers and Bluetooth or Zigbee modules.