RØDE just made recording two audio sources easy with the SC6-L and a couple of smartLav+ microphones. The SC6-L connects to an iPhone through the lightning connector and with the free RØDE Reporter app you can record two people directly in the iPhone.
The SC6-L has two TRRS inputs and one stereo headphone output. When used with the smartLav+ microphones you can record two sources into an iPhone plus monitor the audio from the headphone jack. The Reporter app has many recording options such as split channel and merged mixed audio. The user can also enable/disable direct monitoring, alter boost gain.
The SC6-L can be used with other apps, such as the Camera, FilMic Pro, GarageBand, and Voice Memos. Basically, any app that allows recording audio.
The kit cost $199 that includes two smartLav+ microphones or you can purchase the SC6-L alone for $79.00. If you want to use the system for video and need a longer cord RØDE has a 6-meter extension cable $25.00US