http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMumBvQ1hY%2ffBQj28shxzxZBzLQx%252bcgD8o4%3d

can be made to be on when depressed or off

-- SamsonPhan - 19 Feb 2009

Limit Switch tested by Alfred Frith Limit Switch tested by Alfred Frith Dimensions:0.75" by 3/8" by 0.25"

Notes:

Terminal resistance = 0.5 Ohms

Successfully bent the metal lever arm, hot glued a zip-tie and tested the switch. It should make a fine touch sensor to locate walls

I gave it some strong jolts and various forces, it holds up well. A very small zip tie will be preferable, as they bend easier without subjecting switch to larger forces

Mounting will be interesting, may need to use hot-glue or build pillow-block or something to clamp them down