Well, the NERD and the SeaBear HUDC are the only HUDs that I know of that aren't simply PO2 monitors. Both of them are designed to fit onto a rebreather loop DSV/BOV. Rebreather loops are roughly an inch and a half in diameter. A regulator LP hose is significantly thinner. A mask mount would be even more of an engineering feat.
Provided you sort that problem out, you'll want to find a decent place for the controller box. On a rebreather it's usually velcro'd on to the loop back around your shoulder area. Again you'd need to adapt it to either an LP hose, or secure it somewhere on your harness or jacket. This is how you control the computer, so it needs to be accessible.
They also have a cable for reading PO2 data from the head. I don't know how they are connected to the control box as I don't own either, but if it's a Fischer cable, you'll need to make sure you check the blanking plug often. If it's hardwired, you'll need to figure out what to do with this excess cable that's doing nothing.
Realistically it's a lot of work, and a lot of expense, with very little gain for a non-rebreather diver. The appeal of these smart HUDs is based on the idea that when diving a rebreather you always need to know your PO2. By having a computer displaying not only your PO2, but your deco obligation, depth, dive time, etc., you can free up the rebreather diver to do other things as the information is right in front of his face. When diving recreationally, you just don't need this when a quick glance at your wrist will be perfectly adequate.
That being said, if you want to do it, be prepared for an involved adaptation to OC rec diving.