I've uploaded to Hackage the reactive-banana-sdl library. This library was developed by R. Kyle Murphy(orclev), and I've just added a couple of functions and some documentation in the code. Orclev didn't want to maintain it anymore so I've taken the maintainer role, but I'm certainly not a FRP expert (in fact I started to use the library to learn about FRP), so be gentle...
I have a little typing game called TypeClass, which uses the library. You can have a look at the code, it may help you get started.
There's not that much there, but hopefully this can be of use to some people, and let me know what goodies we could add!
Happy Reactive SDL Hacking!