I just found Bret Robertson's MoreThanNoise website--OK, it was EZ to find cuz he posted a link to it on the Performances/Events thread. But hey..
He's got a very informative review of the Peterson iStroboSoft tuning ap for the iPhone that is well worth reading, even if you don't own an iPhone. Some good info on how digital tuners "work" -- or not.
I was staying at a friend's house without my guitar or tuner. We got talking about Slack key and he handed me his guitar to play. I ear tuned it into Taro Patch, drop-c and Keola's C, but found getting to one of my favorites, Leonard's F, to be daunting sans tuner. I did have my IPad. I downloaded the Cleartone App and was amazed how well it worked with just the IPad mic. Actually seemed more sensitive than my clip-on tuner. Got into Leonards F and wowed them with Puka Pants... Aloha, Allen