Last night I posted a full Instructable on how to extract raw data from the Mindflex toy EEG via Bluetooth (headsets can be bought for $15 on ebay and you need one or two $10 HC-06 Bluetooth modules), and indeed how to make it work pretty much like the more expensive Mindwave Mobile (complete software compatibility as far as I can tell if you initialize the toy with an app I link to in the instructions).
You need to make four solder connections, and jump through a few hoops to set up the Bluetooth module.
Good educational project for those with kids.
Follow the instructions at your own risk. Make sure the headset isn't wired to anything connected to mains while it's on.