I couldn't help thinking about this as I met recently with Fred Hakim the founder of Dalcom Telecom. The company has built a robust IP communications network and manufactures a telephone called DalPhone which is tightly coupled with the network. The phones are based on USB and work with Windows XP.
I found this phone pretty interesting - it isn't the fanciest but it seems to be bulletproof in terms of NAT penetration and voice quality over extreme wireless network conditions was impressive.
In addition, the phone is configured to work with a browser and pulls up appropriate screens based on buttons that are pushed. For example if the phone needs to be recharged, you press a button which pops an HTML page which allows you to enter your payment.
In a demo at TMC headquarters Hakim showed how you could get a phone number (or multiple numbers) assigned to your phone in near real-time and at that point the phone is up and running.
The phones also have unique eight-digit numbers on the back allowing them to connect with one another for free and directly.
The phones coupled with the network are perfect for vertical markets such as jewelry, real estate or any where a PBX is not required and remote workers need access. The company's' solutions also work well for a service provider such as a rural telco looking to move to VoIP.
Other areas where this solution would make sense are dating sites or social networks.
If you are interested in learning more, give Fred Hakim a call at +1(516)466-7733 or send him an email.