Interesting thread! I've spent the better part of my energy in the last 2-3 years doing exactly this.
I'm a middle school Science teacher. I have made dozens of videos "on location" teaching lessons!
I teach a unit on plants. I have a half our show with video, pictures, labels, music, interviews with experts, etc. that shows me walking up on examples of all that we learn. They're filmed on location from various trips that we've taken.
I teach an energy unit, and have a show of my young boys (middle school aged themselves) taking a tour of the Glen Canyon Dam. The students really enjoy this one!
I don't have Geology in my current grade level, but our trip to the Southwest 2 years ago was perfect for those standards. We followed the Colorado river basin the entire trip!
The concept has expanded into a periodic talk show that the students themselves film and star in with me. Our school has built us a small studio with green screen for this purpose.
I have activities planned in class that go along with the video series. This way, the videos become resources that they refer back to many times. More than just a movie to watch.
The movies serve two purposes besides teaching my standards. First, I work in a Title 1 school. Nearly 100% of my students are in poverty and haven't traveled more than an hour from home. So I get to take them along and open the world for them! Second, movie making has become a hobby. I enjoy the filming, but especially the editing.
This summer we are heading to Yellowstone and Glacier. Hoping to film some great things for our animal unit!
