At NAB 2019 in Las Vegas, FiLMiC Pro (the most famous app for full control video recording on iOS and Android, which I have covered in many past articles) announced the FiLMiC Audio app, which can record 48 kHz 32-bit floating point audio and automatically sync Record/Pause with FiLMiC Pro wirelessly via WiFi, even without a WiFi network. Then it transfers and syncs the audio via WiFi with the video file in FiLMiC Pro.
Click here for my prior articles on FiLMiC Pro and stay on my mailing list for more information and my upcoming review on FiLMiC Audio.