I was chosen as the tester, to see how useful an iPad is to service techs. I am looking for a photo editor that will let me write on a picture, then email it. I think it would be nice for furnace change outs to take a picture, add duct measurements and notes, then send to the sheet metal guy and installers.
An engineer customer a while back showed me an ap on his iPad that did that. He used a stylus or pen to hand write notes. Inserting typed text would also be useful.