Phone
Use your phone as a video camera. It is available, you already know how to use it, and you can easily transfer your footage to your computer for editing.
Shoot with good composition. Use the rule of thirds, fill the frame, and set-up a few different shots (medium, closeup, and creative), but stay close to the presenter.
Find a way to steady the camera. Use a tripod, if you have one, otherwise improvise.