You could check iAnchor Lite, I've downloaded but not used it yet. I thought it might be useful to have an anchor watch feature that didn't use much power vs. my chart plotter. I can just leave the phone on charge overnight.
Best tide app for me is Tides Planner by Tucabo, tables for 2013 and 2014 available.
Tides UK will be a good app when more ports are added and the Moon phase is corrected for the N Hemishpere.
Navionics, Marine Traffic, Animated Knots by Grog.
Sky news is very good for weather bulletins, the free iPhone app not the paid iPad one, iPhone app works on iPad.
Non boaty... TomTom and CamerAlert. Starmap Pro. Sun Clock. Google Maps.
Phases of the moon from Universe Today.
Find iPhone. 0800 wizard and Say no to 0840.