Iphone idears Digital jitney

Having had the iphone for a few days now I have had a few more idears about what you could do with it.
The gps is they good and I realised that you could implement a great eco transport tool. To make it work you would need two iPhone apps and a web server.

App 1.

If you want to go from a to b you press the summon button on your specially down loaded iPhone app.
Your origin and destination are compared to a list of shared Taxis running in the city.
If some part of your route matches a near by taxi it is redirected to you. If not fresh one is dispatched.
Your phone gets a Ok response a time a price and expected journey time.
You enter your credit details on the iPhone app and effectively pay over the web.
The journey time is in a range the taxi your getting may or may not change route according to who calls it.
The taxi arrives - its larger than normal and can take 4-6 people.
You share the taxi for part of the route which means you share the cost.
The taxi driver has a Iphone/Tomtom app which is dynamically updated from the central server. It gives directions which it the driver uses to wave through the city to the next pickup./drop off (these can change dynamically).
Taxi drops you off at near your destination.

So what do you get for this.
1. You get taxi like service (origin/destination travel)
2. The taxi may take longer than a pure taxi. - It might stop for others.
3. You get 1/N (where N is the number of passengers ) cost.
So if you imagine that you manage to share the taxi with 4 other people you get 1/4 cost. So an £8 ride becomes a £2 ride - not bad.

The city gets something between a taxi service and a bus service. The taxi doesn't move until someone wants to go some where so you avoid empty bus syndrome. The taxi is fuller than a taxi or car so you get more efficent movement with out sacrificing safety or door to door movement.