I have no idea what I’m getting myself in to, but would it be difficult to make a small shield/addon for a spark-powered device that could give it web access using cell phone networks? Something smaller than a portable hotspot, or that could be integrated in a space-conserving manner optimally.
If so, where would I start?
You can use GSM shields with the shield shield for prototyping and test things out.
Also, we had a few conversation before and you can search the discourse for it 
This thing is really small, and should play nicely with microcontrollers. http://www.adafruit.com/product/1946
I like Adafruit in general but this one puzzles me: That GSM module only works with 2nd generation GSM which in the US is only T-Mobile (and only because they don’t have enough capital to upgrade). A 3rd or 4th gen GSM module would be better.
Is it possible to use a FONA with a Core or Photon because I could not find any library?
It would be a great displacement until I receive my Electron! 