What do you want to track? I like Woman Log pro to note down general milestones, weight, health and make short diary entries. It does sleep, nappies, feeds etc but I've never used that. The pro version lets me email the entries to myself which will be a nice record in future years.
I used to use Nursing to track breastfeeds because it timed them for me but I don't bother tracking any more.
I used baby connect but ditched it as it was causing me anxiety (omg she had 9 feeds and 3 naps yesterday and 8 feeds and 4 naps today...over analyse!). When she started having fewer shorter feeds and longer between poos, it freaked me out.
Well there is the mumsnet app, although the mobile site works much better.
Seriously though, I have heard of an app which helps you find child friendly facilities, days out etc but I can't remember what it's called. And for advice/discussion a forum or even facebook group works much better, and there are loads already. I don't think you'd need an app for it as such, although I'm sure there are already apps or mobile versions of the various forum sites.