If your expected production volume is large > 1kpcs then a 32bit processor with USB host + purchasing the USB stack + learning curve should be with in budget.

If your volume <1k pcs then suggest you get a GSM/3G wireless modem with UART serial output and use a standard 80c51.


Another option
================
GSM/3G Wirless modem with spare processing power or spare processor inside to run your host application.

a)
Telit wireless modules have two options.... Running your application in Python script (checking GPIO's ADCs, DAC, processing SMS's etc) or a GSM/3G wireless module with spare 200MIPS ARM9 processor (all resources free for your application)

b)
Sierra Wireless /Wavecom.... Running OpenAT ... C code - your use application

c)
Siemens / Centurion - Use JAVA to run your application

d)
Motorola GSM - Use JAVA to run your application.

e) + others

Regards
Joe


Joe