I picked up a Line6 Sonic Port VX stereo mic/audio interface for iOS (Lightning) last summer and thought it worked pretty well. I ended up buying a full copy of Cubasis (free version comes with the device) but not before doing some recording with the free one, only to find out that you cannot transfer recordings between them; the only reason I bought the licensed version was for the export capability. Doh! If you get the interface, don't bother with the free version of Cubasis.
I haven't done anything extensive with it yet but so far it's been well behaved - it actually records and plays back. It doesn't seem like much to ask but as mr. Waits said "the large print give-ith and the small print take-ith away". And there is a lot of small print these days. These are a few of recordings I made by the beach last summer: https://www.stecrecords.com/BobSellon/live/CoolThisSummer20170721.mp3https://www.stecrecords.com/BobSellon/live/ItsOnlyLove20170721.mp3https://www.stecrecords.com/BobSellon/live/Something20170721.mp3
In addition to the stereo mic, the VX also has a mono mic, a 1/4" guitar input, a mini stereo aux input, a mini stereo headphone output and left and right 1/4" phone outputs. It's worth noting that the interface can only use the stereo mic, the mono mic or the guitar input at a time. No guitar-and-mic at the same time which is a shame. It's also got a connector for a mini USB you can connect to a charger while using it, a mic gain knob and a "Direct monitor" switch avoid app latency when monitoring recordings. It comes with a little desk top stand but uses a standard camera-screw adapter so it can be used with all kinds of existing stands.