I think what you'd have to do with something like a mower is use your truck pto to turn a hydraulic pump to run a hydraulic mower. The shock of the mower hitting a branch, rock etc could damage your pto if it was direct shaft drive.
There are lots of tractor mount hydraulic mowers available but they would have to be modified to hook to a truck. It might be cheaper in the long run to just buy a used tractor. Visibility in a truck would also be hampered, you really want to see what you're mowing before you hit it.