The Talk-O-Meter has made the tech rounds already, but I had to post it here. It's so simple, and so good.
This phone app efficiently memorizes the speech patterns of two people at a table. It then can calculate how much each person is talking—giving "gentle bio-feedback" when one party or the other is dominating conversation.
So many practical applications for those on the autism spectrum, for whom it can be difficult to read body language indicating when a subject is getting relentless or boring, or when reciprocity would help keep the conversation lively. But I can think of so many situations with "neurotypical" conversation partners where this would be very, very handy...