My first thought was "paying for a second SIM just for that sounds like a pain", but then I read to the end and saw that you're using a service for $8/mo. Had no idea such a thing existed. I clicked through their plans, and it looks like you can reduce that down to $5/mo if you ditch the data plan and select 100 voice minutes / unlimited text. I figure for such a device, you can just connect it to wifi, and don't need a data plan.

I guess it's nice to have the backup, though, in case the local internet connection goes down. The 500MB/mo plan bumps it to just $6/mo.