Mongoose OS now supports cellular connectivity via the PPP-over-serial driver.
See implementation at https://github.com/mongoose-os-libs/pppos.
This driver implements a basic Internet connectivity. Some advanced features like SMS, GPS, are not implemented yet.
You can try it with following modules:
1) SIM5320E 3G Module GSM Modules
2) Adafruit FONA 3G Cellular Breakout
To contact: send us a message or ask on the developer forum.