I'm wanting to implement a health regen option for players to buy and am wondering if I should make it a Gamepass or Dev Product. Either way, it'll be a one time purchase, but I'm not sure if a Gamepass purchased in the lobby Place would work for the other Places in the Game Universe.
Yes, make sure you use the ID of the gamepass and use the PlayerHasPass API.
http://wiki.roblox.com/index.php?title=How_to_Use_Game_Passes
If you wanted to be entrepreneurial, I would suggest that you have a Dev Product, since customers can purchase multiple times, however, the scripts will be the tricky part. I am not sure if you're BC, but only BC members are allowed to sell gamepasses, and everyone can make Developer Products.