I like that math app idea.
I also forget waking at night for WBTB, even when I put the alarm far away. That's why the chair thing helps,and I'd have to set an intention to sit on the chair when I wake up. Another idea is to bring a cooking pan, place the alarm in it, and put a paper on top with "SIT" or "WAKE UP" written on it in big size.(of course, without the pan's cover), or anything creative like that.