Cell Phone chip set

Howdy

I'm looking to embed a cell phone into a product. I don't want a
commercial cell phone, but the chip set. I'm only interfacing it to a
sensor. No LCD, no user interface, so nothing. Size (and cost (and power
consumption)) are the important issues.

I'm starting in smaller prototype quantities, and production would be 1K
per year initially.

I just need a cell-phone chip set that will response to a standard
"phone call" - nothing fancy - no 3G, etc. Should be able to work with
the usual wireless phone companies.

I prefer a chip set rather than an OEM box, but might be interested in
OEM box also.

Has anyone experience in making there own embedded cell phone or
represents such a chipset /oem box manufacturer?

Thanks.

Thanks