Smart Phone Apps

Been wondering lately about which Db meter app. to download on my Iphone and figured I'd throw the question out there to all those in the know. Might as well ask what other valuable audio apps are any of you using on your Iphone/Android? Maybe this information will be of some value to others or maybe I'm the only one who's still ignorant about this stuff ( which is often the case). ;)
Wasn't sure which thread to post this in so if I'm in the wrong one, moderators feel free to relocate as required.
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