Well first thing is first, you have to download the TI-83 programmers manual. What you're looking for is the hardware layer specifications for the link communication port and obviously the software specifications on how user programs can use it. If you can find the hardware specs I should be able to point you in the right direction at least, a micro controller may not be required, it's possible with some simple external logic you could have the TI communicate directly with an RF module, but I'd need to see the docs for it.