Should be possible!
Are you aiming for a full client with blockchain, or a lite client which connects to a central server?
I think it should be depended on how a device connected to internet? A full client with blockchain would be more safe but also consuming more power and bandwidth. A lite client could be more energy efficiency and need not always connecting to the net, but will provide more security.
Either way, the big obstacle for any of those approaches is how to get online. Reading "gsm included" means hassle and costs for a sim card. Have something with wifi instead? Then you will not have internet everywhere. Or only internet when doing a transaction, aka mesh net or the POS as a relay? You better be sure the data you receive is not forged!
But besides all that.. The hardware should be strong enough! :-P
For a mobile solutions GSM seems better then Wi-Fi, at least outside some big cities. Therefor sim card/GSM might be the only choice. Furthermore, it's possible to use open-source GSM platform like OpenBTS
as it's access point.
Must say I'm not an expert in GSM, any suggestion/commentary would be great.
some links:Can you hear me now? – OpenBTS – Open Source GSM base station. « @ggregatorBurning Man's open source cell phone system could help save the world