Is it possible to get the external Magic Trackpad disabled automatically while I'm typing?
I do get a lot of cursor movements/clicks when just touching the trackpad accidentally.
If you mean the built-in trackpad, then you cannot disable it. But you can disable it if you connect an external mouse to your Mac.
To do, just open System Preferences > Accessibility (or Universal Access) > Mouse & Trackpad > tick on Ignore built-in trackpad when mouse or wireless trackpad is present