It comes with a SparqeeSIM card, and their plans are actually very cheap if you send very little data. And unlike a few other solutions, it works almost everywhere (with increasing price though): http://www.sparqsim.com/
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I'd be interested in learning what product that is, if you can share that with us? :)
One alternative for 2G/3G connectivity is SparqEE CELL, it seems pretty easy to work with over UART:
http://www.sparqee.com/portfolio/sparqee-cell/
It comes with a SparqeeSIM card, and their plans are actually very cheap if you send very little data. And unlike a few other solutions, it works almost everywhere (with increasing price though):
http://www.sparqsim.com/