Heh, I have had GREAT success doing the following
Take a simple C clamp like this and use a couple small bits of cardboard or leather (I use leather) so that the clamp doesn’t mark your guitar’s neck/finish and clamp it to the neck where a magnet device would normally sit.
Once you’ve got THAT setup, I just clamp my phone to it using a couple very cheap spring clamps like these.
It gets you unreasonably good video angles for pennies. Definitely not as clean and nice as the magnet, but while I wait for my kickstarter package to arrive, it’s a very reasonable and workable alternative.
Here’s my actual setup, only with an old crappy Nexus instead of my current phone which I used to actually TAKE the pictures… anyway, hope this helps.
Edit -HAH I just realized I have the phone on the wrong side of the clamp. It’ll get excellent footage of my shitty fretting! Anyway, you get the idea I’m sure.