I've been in a hotel room that only had a motion detector as the means to turn the bathroom light on, and it didn't have any type of manual override. The light would turn off if you stayed in the shower too long without much movement!
Bryan P. Holland, ECO. Secretary - IAEI Florida Chapter
Use those on bathroom remodels when there is no way to get new wiring to the bathroom without a lot of wall cutting/patching. Last time they cost $26.00. Not my favorite thing to do but they are useful