Glidewheel - New sensor from Mindsensors
Mindsensors have updated their 'coming soon' page with a little teaser. It's called the GlideWheel and it's an rotation sensor for those motors that don't have them already built in. From the very brief description on their page, it looks like it fit nicely witht he Power Functions motors and the older RCX motors. I know a lot of robot builders love these motors for their size, so it'll be fantastic to be able to control their position.
From the only picture, it looks an axle through the middle is all you'll need. That could also be handy if you need to keep track of the rotation that is not directly on the motor.
From the post:
This Device will have several models -
One model will allow you to connect PF Motors to NXT Motor port. It will have encoder support to control them precisely.Second model will be similar, for RCX motors. Third model will be a digital angle sensor, to measure angle with 1 degree precision.
Mindsensors - Coming Soon