Best (Simplest!) Long Exposure App

[roscoetuff]

Looking to do some long exposures. Dawn, dusk, night, moon.... all of it.
Saw there's an iPhone app... and pulled one, but it's stuck in New Zealand and that seems a bit of a pain since that seems to be the default (LExp's the name). Curious what folks are using... if they're using anything at all?

 

[Prest_400]

As far I've read about photographers doing long exposure, most tend to work under guesstimation and settings fine tuned through trial and error.
Fred Parker's exposure guide is certainly very useful.

I haven't done as much as I'd wish, and often tend to shy away of Slide film despite Provia being excellent reciprocity wise. There was some consensus that it's hard to overexpose night scenes.
Oh, and reciprocity. I've used Portra 400 which Kodak calls for testing after 2 seconds or so, great! There is a log formula posted on LFF about it. Seemingly it benefits from a couple stops correction at 10+ seconds.

I'd like to test Olympus EM5's "live" long exposure mode, which shows how the image is building up.