These are chat archives for Nethereum/Nethereum
And then here's my own test-grid for C++ cross-builds on a myriad of resource-constrained devices (https://github.com/doublethinkco/cpp-ethereum-cross), which overlaps with John's list. We've collaborated a lot. I got a grant recently for continuing that work (and getting started on Light Client for C++ soon) - https://doublethink.co/2016/02/23/we-have-blockgrantx-funding/.
The more powerful SBCs run OK as full node, but only just, and anything weaker is constrained to JSON-RPC to a trusted full node for right now, until "real" Light Client protocol support is added. Zsolt has been working on that for geth since last year, and it will start to land after the Geth-1.4.0 release. But that's the only implementation which has even be started yet, to my knowledge. And then my C++ one will be number 2.
That full "Project ADEPT" vision will need real Light Nodes for truly autonomous Edge Computing scenarios, but JSON-RPC to trusted nodes will be a good stop-gap: