RF advice sought! On-off switch from scratch.

My goal is to basically mimic the common "RF item finder" key fob-like devices that beep when you push a button remotely. I don't have much (read: any) RF experience, and I know what I'm attempting to do is like reinventing the wheel, but my design needs to be "from scratch" so I can get it to fit in a specific form factor, and so it can be just as cheap as the cost of components.

I have done some research, and think I should either work at 318MHz or 433MHz, because there seem to be a lot of pre-made daughter card-like modules out there that are antenna-in, data-out solutions at those two frequencies. Unfortunately my form factor and price requirement prevents me from using those pre-made solutions. My plan is to go on Digikey, find some cheap RF transmitter chips and receiver chips that have application notes and application circuit diagrams, and just follow those. My choice for a receiver right now is the Micrel MICRF002, and a MICRF113 for the transmitter.

My form factor goal for the receiver is something about the size of a CR2032 battery, but obviously taller than the battery for everything to fit in. My form factor goal for the transmitter is much more allowing, and can be reasonably large as to allow for a good amount of transmission power and antenna size (about the size of a TI-83 calculator). I'm thinking of having a coiled wire antenna in the transmitter, and a PCB trace antenna in the small receiver

Does anybody have any advice for a from-scratch _simple_ design for an on-off switch controlled by RF? Any words of warning before getting into RF design?

Thanks

There are many small-size key-chain transmitters and a bit larger receivers on the market. To operate over a distance, you will need at least a quarter-wave antenna, not a "coiled wire", and not a PCB trace.
I would recommend you to start with an available version, then if you can operate it as desired, you can remake or miniaturize the transmitter or receiver. The start into RF design usually requires experimenting. You will learn how RF things work, and this will help you to get good results.