Decided to utilize one of the Cansmart circuits, soldering a "pin" to the K2's yellow trigger wire, and plugging it into the white wire on the three-pin Cansmart plug. The "pin" was a piece of one of the three claws from a spring-loaded retrieval device. I'll post some pics next time the seat comes off.
After a couple of rides, I was able to access the files on the Innovv K2's DVR. To do so with a Motorola G6 (Android), you have to put the phone in airplane mode and sync with the "Innovv K2" wifi connection. So you don't have phone service while connected to the DVR. Innovv said they are working on a fix and there is beta software you can download. (Their Em responses were same day, considering geography.) I don't know how IOS systems would work with this unit.
This and other dash cams are mainly intended to have a visual record in case of accident. With the K2 (and maybe other makes), you can have a live feed from the DVR on the phone screen while riding, about 60/40 front/rear. The rear view should provide good additional rearward visibility. Many thanks for the feedback I've received in this post.