Kinda unrelated to the whole Rpi discussion, but the SOC of any phone that runs Android would do. If that is Linux'y enough for you then it could be a solution. The problem is sourcing the SOCs. Spreadtrum makes some nice chips that include app processor, cellular, WiFi, Bluetooth, etc. for ~7$ but they're not for sale if you're not an ODM.

This is a great article [1] about how Chinese SOC manufacturers and Chinese IP works. I ended up just ripping out the mainboard of phones to get access to the SOC [2].

[1] http://www.bunniestudios.com/blog/?p=4297 [2] http://janos.io/