Which I've used, but it's a PITA rather than any real aid, especially w/o an Android phone. It also slows down and mildly annoys anyone who is calling you (maybe not a bad thing, but certainly not the same thing). And it's only really useful for people not in your contacts list, which is probably significantly less than 1/2 if you're not using it for work.

Plus, anyone not annoyed enough will still make your phone ring every time they call, demanding attention now to at least see who called. But I could do that before, with caller ID.