Hi Nathan...To the best of my current knowledge, there are no 'official' IPhone Blitzortung Apps currently available...that work. There are multiple reasons ... a massive server upgrade, and resulting database issues from new processing algorithms last fall.. Google's change from Free Maps to 'Credit Card Required', and some Legal protests to Apple a couple of years ago because of improper / unrestricted access, and some unauthorized data access from a couple of large 'organizations' have resulted in changes to raw data access for non-operators, and certain types of 3rd party usage.
The 'best' applications are going to come from a legitimate operator, or associated approved 3rd party with the right skills and permissions to apply for Non-Commercial use.
Meantime, suggest simply access
https://www.lightningmaps.org/?lang=en#
or one of the maps on Blitssortung, e.g.
http://en.blitzortung.org/live_dynamic_maps3.phpattached