My goal is for it to be as hidden as possible, whilst still giving me a nice quality video.
Currently my best option is the Mobius camera. The reason being I ca detach the lens and reconnect it with an extender, as you can see here:
It's possibly still a bit too big. But this is only $100. I'm willing to spend ten times that amount if I can find something smaller, lighter, and more professional. Being able to detach the lens like this is a requirement, but it doesn't matter how big the other components are as long as the lens itself is small and flat. I can run a wire to the other components.
I was also thinking of removing a modern phone camera, but that sounds more complicated that just using something that's been designed for this.
At the very least it should be able to shoot reasonable quality 720p (but the higher the better). If we have things like a GoPro for just a few hundred dollars, there must be things like this on the market, right?
I have a limitless budget so give me the absolute best options out there.