I bought a Maryland Gun Works (MGW) M&P sight tool, aka a "sight pusher," which is the same one the OP is asking about. It can be used to move the front sight or the rear sight -- there is a small spacer plate to set it up right for whichever one you are doing. I have used it to swap out front sights, and to install Warren Tactical sights on the rear of my M&Ps.
The drawback of these is that they only work on one type of gun, e.g., mine is just for the M&P. This one does not work for the Shield, but I am thinking about hand-crafting a small plate that will allow it to work with the Shield (I'll bet the company eventually adds this capability to their product).
The MGW Sight Tool cost me around $120. (There is one on eBay right now for $119.00, at
MGW Sight Adjustment Tool Pusher s w M P New | eBay).
I strongly recommend using a good quality sight pusher like one of these, over using a wood block or steel punch to remove or install sights. Used properly, it ensures there is no damage to the sight or the pistol. And it allows adjustments to the sights to get them dead on right.
In other words, if you are going to install (or adjust) one M&P sight, perhaps it is best to go to a gunsmith and pay. If you want to do it more often, buying a MGW sight pusher is a good purchase that might save you money as well as give you control of the process.
Full disclosure: I have no equity in MGW or any vendor selling MGW sight pushers.