Does anyone use a TTC app on their smart phone?

I had no idea these existed until a friend recommended a cycle tracking app called Glow. It kind of blew my mind - it's like FF but much prettier graphically. It's free, tracks your cycle, gives you health tips, lets you record your weight/mood/symptoms/BBT, etc. See article here:

But now I'm wondering what other technologically-savvy bees use - are there other apps that compare?