Immersion isn't specific about the damages it wants, but they could easily be far-reaching when vibration feedback is at the heart of much of Fitbit's current lineup.

We've asked Fitbit for its response to the lawsuit and will let you know what it says. With that said, it's likely that Fitbit will fight the cases tooth-and-nail, or at least try for a low out-of-court settlement. This is business as usual for Immersion, which has a tendency to sue virtually anyone who makes a device that shakes, but Fitbit can't really afford a major defeat. The company only made about $299 million in revenue in its latest quarter, and turned a $34 million loss -- a significant payout to Immersion would be painful enough that it could hurt Fitbit's chances of bouncing back.

Update: A Fitbit spokesperson has responded.