We have heard quite a bit about Android manufacturers having to pay per-device licensing fees to other companies, but the Android manufacturers turning the tables on others is almost unheard of. Occasionally, though, they score a big break like Motorola did in a European case against Apple. The Google subsidiary won an injunction over a basic 3G patent, and are now trying to put it to work to get as much as they can from Apple.
How much, you ask? Well, in addition to temporarily taking Apple's 3G devices off the shelves in Germany, they are seeking payment of an additional 2.25% of the revenue from every 3G device Apple sold, ever. Doing some math will reveal that if upheld, Apple would owe Motorola 2.1 billion for past devices, and royalties for any future products.
Of course, there is almost no chance that Motorola will be granted their request, even if they reduce their demands. In fact, Apple is already appealing the ruling in question, and it just doesn't seem possible that they would ever stand for paying out so much to a competitor. Still, many manufacturers pay Microsoft royalties for their devices on some questionable patents, so I suppose it's not completely outside the realm of possibility.