I only do weight because he's huge and I'm curious. But I take it with a grain of salt because our weighing system is quite unscientific. Recently we can sit him down on the bathroom scale and that works, but before that it was the ol' hop on the scale with him, hop on without him, subtract, method.
I track in the webMD ap. It's got a cute baby book section that I like to put pictures in for firsts and it reminds you to take a pic each week. IT might be late to get started on it but you can at least track the measurements if you want to.
it's also got the timers, but I never used them.