Not sure about other OSes, but I occasionally use a Wacom Bamboo Pen&Touch (CTH-470) on Linux, and I have it set up to do exactly that. It's really easy to conf

Not sure about other OSes, but I occasionally use a Wacom Bamboo Pen&Touch (CTH-470) on Linux, and I have it set up to do exactly that. It's really easy to configure it with the KDE settings plugin thingy, but I think that just talks to the Linux Wacom drivers, so it should be possible to do something like this with other DEs too (if it isn't even the default). It's also trivial to set one the hardware buttons to do sruff like send Ctrl+Z or toggle the touch input on and off, which is nice. Plus, they're really cheap to buy used, I bought two for like 15€. It's not without problems, I personally don't like the pointer speed / acceleration, scrolling and zooming are way too sensitive, and palm rejection isn't too great (it pretty much just disables touch whenever the pen is near the surface). However, I have put exactly zero effort into customising the first two things, so these might be fixable, and for me the latter isn't a huge problem because I don't use the pen and the touchpad together a lot, so having a toggle button as mentioned before works just fine for me.