Just got an iPhone too weeks ago. I feel like I just came out of the stone ages. For $7.99 Navionics Marine & Lakes is amazing. Charts,tides, currents, POI's. Not a substitute for a chartplotter because of screen size, not weather proof, battery life and in general not as rugged as a dedicated chartplotter but still great.
Accuweather's radar maps, seem to be pretty up to the minute and free.
Knot Guide, also free. Not animated butstep by step guides for many, many knots. 30+ sailing knots.