In an experiment of Jeroen van de Ven participants made a selfie, using the webcam, which was made available to another participant. Step 1 is that they make a photo; if they are satisfied they save the photo (step 2), if they are not satisfied they can try again. The experimenter can see the photo that is saved (verify_snapshot.php), and in case the photo is unclear the experimenter goes to the participant and asked him or her to repeat the procedure. Download the files here
Note: this works in Firefox. In Google Chrome this will only work when using a secure connection (https instead of http); on the moment creedexperiment.nl is only configured in non-secure mode.