A few months ago I wrote about the UART on the Nexus 4. I’ve been talking to some people on IRC lately and it seems (unsurprisingly to me) that the Nexus 7 2013 has this port too and so will the Nexus 5.
I’d go as far and compare this to be potentially at least as useful as ‘The Other Half’ on the Jolla Sailfish smartphone. It’s a fast local connection for advanced peripherals. Only your imagination is the limit.
Well, and it’s a very handy debug port for bringing up a modified kernel or a new operating system. In that context. I’ll have to try it on my Nexus 7 2013 LTE which is due to arrive here tomorrow.