For tooth brushing, my kids use the Timer+ app on my phone which has ads unless you upgrade. I keep forgetting to upgrade it but the ads are inconspicuous enough not to bother me. They're usually for games and grocery items. Last night after the kids had gone to bed, I walked into the bathroom to get my phone and saw a full-screen ad with a naked woman and a Snapchat logo saying "Hey do you want to f***?" Needless to say, I was furious. But at least the presence of the ad meant the kids didn't click on it and see even worse content. I deleted the app and am now waiting for Christmas for the kids to get their electric toothbrushes with built-in timers.