This is something I had previously suggested (don't feel like trying to find the older thread) but I still think it's a great idea, especially for use with Google Voice. At the same time, I would not get too excited about that particular service. I tested it with several numbers that should have returned a response, and it returned nothing on most of them, an incorrect entry on one (and they seem to have no way to report errors), and maybe one or two actual good results. Plus, if you read to the end of the referenced DSLReports thread, even there it seems they are wondering if this is a usable service.
But still the idea of being enter a one-line lookup of the form http://some_address?variable where variable contains a ten digit phone number, and have the device display the result of that lookup would be better than nothing, which is what we now get from Google Voice.