ISM band : 900MHz. **broken link removed**
The site shows LNA, VCO, Mixer, VGA...receiver.
You'll have to add a PLL (which you'll buy) to control the VCO
You'll have to create the FSK modulation on your own...
the project will be difficult because i think you'll need to build each block individually and test each. then add all building blocks together.
UCLA also has built a discrete transmitter / receiver that i've seen on the internet.
i'm not sure what kind of commitment you want to put in because if you build a system from a schematic, it still may not work...let me know.