Testflight link

app/developing.md

@@ -19,5 +19,14 @@ If you are able to create debug logs and create Issues feel free to subscribe th
 
 ### iOS Testflight builds
 
-* not yet available. Meanwhile, please use [Xcode](https://developer.apple.com/xcode/) to install the app on your iOS device.
+**[https://testflight.apple.com/join/oqZhY70M](https://testflight.apple.com/join/oqZhY70M)**
+
+ ⚠️ Please note ⚠️ We've got a lot of trouble pairing with the card10. If your want to connect to the card10:
+ 
+* checkout the [ios-workarounds branch](https://git.card10.badge.events.ccc.de/card10/firmware/tree/ios-workarounds) of the firmware repository
+* rebase the branch on the current firmware master
+* build a firmware image
+* flash that image on the card10
+* The ios-workarounds branch basically exposes all characteristics publicly, so everybody can connect to your card10 and read / write characteristic, so this is clearly only a development helper and not ment for day-to-day usage
+