A secondary SIM card costs about 5 - 10 EUR here in Germany, is it that much more expensive in your area?
That's more than the costs added to the device when we put that at the side
Additionally, a SIM card is stolen pretty fast if you can remove it that easily.
It doesn't work if you have a subscription.
I would like to take a subscription with 20go of data and unrestricted call and sms. I would use a feature phone with a secondary external SIM port, so that I would use the phone to call etc and the Pyra when I need data.
If someone want to stole something, he would rather steal sd cards instead of hardly remarkable and unusable SIM or the whole.
According the pcb photo, 3G module is on the side so it would be easy to do it, I like the idea of being able to change SIM as it is a simple card.