Hi Nigel,
Thanks for your input,
Yes I understand that the power is going to be high when transmitting, I do think that 16mA is quite high for idling, the SIM900 is 22mA!!
All I really need is a TCP/IP Stack, and I have had a quick look at some GSM chips which don't seem to have one on.
I would shut the chip down, but I want to retain GPRS connection as it can take too long to reconnect sometimes.
It will be run off of a 12V leisure battery charged with a solar cell, the solar cells are quite big for high current, so I want to try and reduce the power consumption as much as possible, to reduce the cell footprint. I will probably use something like a 4700uF "super cap" for the inrush spikes.
If you have any suggestions to which GSM chip or a handful of chips I may look at then please do let me know!