It's finally been proven: the Mitakon Lens Turbo Nikon G/Ai to Micro Four Thrids (MFT or M4/3) works on the Blackmagic Pocket Cinema Camera! And judging by this short sample footage - it's not even bad at all, especially considering the pricepoint. This focal reducer sells for around $140,-
[UPDATE April 2014 - Mixed reports are still coming in, buy at your own risk. It fits for some, it doesn't for others.]
You can find plenty on eBay.
I'm planning on getting one in the coming month(s) as well.