Hi, Just downloaded Grolog - an iPhone app. There's a few similar apps out there, another one's called Perfect Hydroponics.
Grolog looks pretty good, it has setting parameters allowing you to record upto 12 nutrients and additives (so its useless if your'e running Advanced Nutrition!), and measure everything possible, temps, humidity, lighting etc.
Once the settings are in, running a grow is pretty simple. You can start a new event / day, take a photo, and enter all the details you want.
You then have the possibility to check back through archives, plot graphs, and make reports of your grow.
This app looks nice and clean, whereas 'Perfect Hydroponics' seemed a little too basic and I didn't like the layout.
I'm getting started with a grow soon, so I will update this and let you know how this app helps me, but if you're already growing, why not share your experiences!