Kir Kovalski, who brought us the awesome Noizio app, has launched a simple but useful tool to check how your app icon looks on tablets and mobile.

This website has unfortunately been redesigned or gone offline, so I have removed the direct link to it. The screenshot below hopefully preserved enough of the design but if you are really keen to inspect further, try this Archive.org link. FYI: the site was first featured on 04 June 2015.