Very useful post, thanks Harlequin. I'll see if that app works for me, sounds like just the thing I've been looking for.
I've found that depth of field isn't always desirable - if you want to really foreground something for example - but in general it does make a huge positive difference.
Thanks for link to the app
I generally use a custom script on my Canon that shoots from the current focus up to the hyperfocal length of the lens then stack in Photoshop CS6 but it will be handy to use the phone if I've not got my full kit with me