Evernote is a great place to store raw info and pics while performing an estimate.
I usually go into an estimate with Evernote open on my iPad.
It beats the heck out of fumbling with
SM Mobile in front of an important customer.
Facebook Pages is pretty good for iOS. It helps manage your FB business page, complete with instant notifications.
Wunderlist is a great place to keep a running list of needed supplies, etc. You can share lists too. Mel likes to add to the list when in standing in the checkout. Everything comes into the shared list instantly.