Vinod made a Qi wireless power receiver using Attiny13, that is available on GitHub:
I have only two aims while trying this. The receiver should get powered by the transmitter continuously. I should be able to control the power received by adjusting the error packets, in my case I am trying to keep received voltage always 10v.
There are lot more but I am only interested in this two features for now, so I will not be following the complete Qi specs described on the WPC documents, by the way, it worked for me without any issue. This is purely experimental.
See the full post on his blog.
Check out the video after the break.