can this be done? angle detection of object

I was looking for a solution for the following:

I want to create a device that would detect and give feedback about alignment. In a perfect world, I would mount some sort of device/reflector/small sensor on a flat piece of metal and want a remote sensor to tell me IF that piece of metal is aligned with a remote sensor from about 3 to 20 feet away.

If this can be done, the piece that is to be mounted has to be very small and unobtrusive. Further any deflection of angle from absolute “square to target” must be detected by remote sensor and in a perfect world (much the way a guitar tuner works) as the angle of deflection moves left and right, a series of LED’s would lite up to give "feed back " to align the metal to the sensor such that user could ensure that he is aligned square.

Does this make sense?? Anyone with any ideas…?