There's an app for that - it's called, succinctly, "dashcam for your bike". They sell clip-on phone holders for your bike and do some image stabilization in the video they record, and have integration so you can report people/items blocking the bike lane to the local infrastructure. Would recommend.
Heh, full disclosure: I was in a startup program with the dude who makes it so I'm def biased, but in Pittsburgh they put bollards on a road to establish separation for the bike lane with credit to the reports from the app giving them historical tracking on how prevalent it was. So yeah, reports may not send out someone posthaste, but they can improve the situation for sure.