There won't be any issues if all you're doing is tapping power off the connector. But if it's a full blown wiring harness connector, including the data lines, the unterminated ends of the wires may cause problems with OBD communications...
No issues with mine and works great.
Auto shut off after 5-10 minutes so it doesn't run the battery down. Powers up when you open the door and has a built in shock sensor that starts recording if you car gets bumped.
Got it off Amazon.