I think you should write it.
All it needs is a simple python script to run in the background.
I haven't messed around with the RPI yet but I've been interested in it to use in conjunction with an arduino for a bit of a fancy brewing setup. Speaking of which I personally think an arduino would be a better option for what you are looking for.
If I find anything I'll let you know. Thats the best I can do for now.