I so desperately want this, I think about it about 5 times a week and probably mention it to my wife as often. But in my old small house I doubt I could ever get one set up. Much better than a touch less one.
I bought an one that attaches to the source line to the faucet, but I'm nervous to install it for risk of leaks.
It's just a standard plumbing fitting, and it engages with the plumbing below your actual faucet. Space shouldn't be an issue?