ASP would be reliant on being being connected to the internet at all times right? I dont think this is possible.

WIFI would require the Salespeople to have an available internet connection nearby such as at home or a hot spot? Would probably be inconvenient.

I presume PocketPcs cannot just connect to the internet standalone.

GPRS sounds more interesting can this be active anywhere at any time?, how would the central database receive the GPRS sent data?