What's your use case for the tracker. As SciFan said, Star Walk will show satellites; there is even a search mode for them. It should work fine for spotting.
However if you need an app for something like line of site tracking, like for Amateur Radio satellites, you'll probably want something like GoSatWatch. I just downloaded this, and it looks pretty good. As good as anything I used back when I was playing with PACKET radio and satellites. Admittedly, that was quite some time ago.
Yes, $9.99, but it appears to be a quality app. Good reviews, and I like the options I've played with so far.