Google Voice is more useful in theory than it is in practice for me. If I had multiple phones to manage, it would be great to have one number that could ring them all, and a centralized voicemail system to unify them. While voicemail transcription is marginally useful, I don’t really get all that many voicemails, and hearing the original audio via visual voicemail is already pretty convenient. The fact is that most of my calls go to my cell anyway, so routing them through Google Voice first is not of much utility.
On the other hand, faxing seems like it should have been replaced with something better (like, perhaps, email?!?), but is still widely used despite its relatively archaic technologic foundations. Most people don’t have a fax machine of their own at home (or, increasingly, even a phone line). This requires resorting to paying someone to use their fax machine or slumming off of the work fax machine, which is clearly a suboptimal solution (even if it’s generally accepted or at least overlooked).
What would be better is an online service which could route documents to those who still rely on fax machines. Even better, this service could provide a virtual phone number (much like Google Voice does) that could receive faxes and email them to you as PDFs. Services like eFax have the right idea, but are not free and, at least the last time I tried, require a special viewer app. This is the kind of problem that Google could solve. Well, Google, are you up for it?