I still use bearing buddies. They're inexpensive and better than a regular cap I think, just not a replacement for maintenance. Still have to take them off from time to time and repack. Once a year is fine unless you tow a lot.
You are supposed to be able to pump them up and the spring in the cap will keep the hub pressurized, preventing water from entering, but I've never seen that actually work for any amount of time. They have a relief hole that prevents you from actually forcing any grease into the bearing.