We've recently been pushing the low cost Raspberry Pi Zero to see what it can handle.

With a custom Raspbian linux build with real-time patches, Martin Evans ( @lostcaggy on Twitter ) has managed to get a slightly modified version of Ardupilot up and running on a Pi Zero controlled RC buggy using our (Dark Water Foundation) Escape board to control the motor and steering servo and transmitting video, GPS and IMU details back to QGroundControl.

The Buggy is being used to test the hardware and software before it's loaded into a boat (old used Kayak) and sent out to survey the oceans (probably closer to shore though :) ) - https://hackaday.io/project/12484-the-julius-project

Above is a short video showing its second run.

The Escape board is currently on Kickstarter - ending very soon.