Pressurized fermentations are becoming increasingly popular, and for a good reason. Some of the benefits that you gain from fermenting beer under pressure are: Lower ester production, being able to ferment at higher temperatures without producing off-flavors, and having your beer carbonated by the end of fermentation (rather than carbonating separately for over a week!)
To be able to ferment under pressure though, you will obviously need a fermentation vessel that is capable of safely handling these pressures. These specialized fermenters are also refered to as "unitanks" and, lucky for you, we have multiples to choose from! Below are some fermenters that are actually designed for pressurized fermentation, including the Fermentasaurus, The Blichmann Cornical, and the WilliamsWarn BrewKeg. Other products that you'll need include a CO2 tank and regulator, the appropriate attachment fittings, tubing, etc.