Thoughts on an app to track order of people waiting for bathroom?

Happened to me multiple times to wait for a bathroom, and people cutting in front of me because they didnt know there was a wait. Thought of an app where you scan a QR code by the bathroom and join a virtual line, and you get notified when the previous people are done. Would be first come first served, and you can leave the line whenever.<br><br>Would be free to use, and there would be ads every time someone joins the line.<br><br>Dont want to spend time developing it unless people think its a good idea, so let me know.<br><br>Edit: seems like there are a bunch of apps like this already. This would just be a simple version with minimal features, and free to use.