I have a similar project going on at the moment.
Its using a radio frquency, much like an keyless entry vehicle and keyless start kind of thing, but acting in a home lock system.
Yea the programming aspect is not too difficult at all, and since you have java experience, picking up the programming in c wont be hard at all.
I would recommend looking into the parts you want to use and post em up. Theres more advice to give once you get started