any plans to accept other SIM cards?
Now that I've been schooled in the variabilities of SIM cards and carriers, I can answer this with a little more authority.
We can support SIMs from most carriers, if not all. However, the APN for that SIM/carrier has to be entered in the firmware first. It's a sort of a circular problem, because, lacking any local programming ability, the firmware is updated over the air, which, duh, requires an APN and SIM for a working carrier to be installed to get the update for a new carrier's APN.
So, we can't just send out a unit and have someone install their own SIM in it without preprogramming the APN into the list, and testing it. We went through 3 or 4 weeks of angst with one M2M data company whose system works differently from the other 4 or 5 we've tested with. It took a firmware patch on our end to get it on the air.