It depends on what type of PPM meter. The European PPM's (black backgrounds) are really cool, but confuse most jocks and board ops because they are looking for the red line at "0 VU". If you want your folks to run their levels correctly, straight PPM's are probably a mistake. Boards like Harris, SSL, and a handful of others, have a horizontal segmented VU with peak bars. At least that allows for average VU readings too.
For external/augmented meters, I recommend the Dorrough VU/PPM meters. You can usually find a used set on FleaBay for not too much money.