My thinking was to use the PIC on the main board for those who would rather not use PICAXE. I think the latest PICAXE chips are the 18M2 and 28X2 which are custom made PICs which I've yet to see datasheets on - I just started this yesterday. Since I know a smattering of PBP, I'd rather go that way.

I was drawn to this by the ultra-low cost educational potential of the XINO basic board. If they can modify the bootloader (and add current limiters on TX/RX) this could be powered from a USB port, a crank-style generator or a solar panel. A PIC on the shield would add cost - I'd prefer a ??KB I2C FRAM as an option to store AT codes. FRAM gets costly above 8KB or so but it's non-volatile. It would be more work to code but I assume you are hereby volunteering...

You could have a bare-bones development system for $6.84 (Xino kit) + $2 (PIC16F88) or for those with deeper pockets $2.25 for the PIC18F25K20. Of course, they also will work with Amicus18 main boards although w/o the small customization tweaks I think we can do on the Xino board.

I've asked about doing an XRF shield which I think would have enormous potential. I've finished these (except the details awaiting the long-promised Tibbo EM500/GA1000 firmware) and need something to do this afternoon.