Young's double slit experiment - homemade I want to do the double slit experiment to demonstrate the particle-wave-duality to people outside of physics.
I can do it on paper and try to explain the maths and physics behind it, but it is a dull thing for non-physicists without a demonstration. 
Building the slits and using a laser to show the interference pattern is easy, but how do I realize the 'measuring device', which detects through which slit a photon went?. What kind of apparatus does it take?
edit:
It seems I wasn't clear. What I'm trying to achieve is to display the interference pattern of the wavefunction and then let it collapse due to the measurement of which slit my photon/electron/whatever went through.
 A: It is easy to observe the patterns on a screen. Veritassium made a very nice video of Young's original experiment. Even easier if you use a laser.
Or directly, watch the pattern on your own retina by holding a slit (or pair of slits) just in front of one's pupil. Then look at a sodium street lamp or at Christmas led lamps in different colours.

Source
For a permanent record, one can use the sensor of a dslr (digital single-lens reflex) camera. Remove the lens, just use the body. Or one could use the body cap, drill a hole, cover the hole with a double slit and watch the pattern. That is how I made the images in this composite:

Source 
The collapsing thing is difficult to show, though. You can close one of the double slits. Or manipulate the polarization of one of them.
A: You can get the which path-information via the photons polarization, just put polarization filters (e.g. from 3D cinema glasses) with 90 degrees relative rotation on each slit (let's call the orientations 0 degrees and 90 degrees). You can decide to use this information via a third polarizer in front of the screen: if its orientation is 45 degrees, then you don't have the path information at the screen and you see the interference pattern, but you don't see it for 0 or 90 degrees. See also Quantum Eraser Experiment.
