[PhotoJim]

This is an interesting idea, and it has some practical application.

The stumbling block, I suspect, is that cell phone frequencies are regulated. You can't just put up your own service on the 1900 (or 1800) band (or 850 or 900 for that matter) because you don't own any spectrum. You'd have to get the carrier's agreement. That would require efforts to ensure that your cell site wasn't interfering with the service of other customers.

WiFi, conversely, is completely unregulated and you are free to reasonably interfere with your neighbours. The spectrum is public domain.

I know I'd be annoyed if my neighbour's cell site made my service less good at my house. In dense housing like apartment buildings, it'll be even more of an issue than in my neighbourhood of detached bungalows.

The only way I can see this being viable would be if someone put out equipment for GSM service on a public domain frequency, e.g. GSM 2400. Of course, that would mean we'd need phones that supported it and you'd have to persuade your provider's SIM that you could "roam" on it.