device information

I am looking for some position/speed sensor detector device. It only
needs to work within 40 cm range. In term of position detection, I do
not need super accuracy. Any advices will be appreciated.

<ask8y@yahoo.com> wrote in message 
news:1186766878.039175.315120@x40g2000prg.googlegroups.com...
>I am looking for some position/speed sensor detector device. It only
> needs to work within 40 cm range. In term of position detection, I do
> not need super accuracy. Any advices will be appreciated.

Half metre ruler & stopwatch?