I have an NSI pump. It is self-contained with a 12V battery and you can regulate the pressure. It will turnoff automatically once it hits the preset pressure. However, I think the OEM battery is a piece of junk. I used to be able to pump up several kites off of one charge, now I can only pump up one 20M kite before it needs a recharge. I am going to buy a replacement battery. Some of my friends have experienced other durability issues as well. When it does work, it works great. You can do other things like setting up your lines if you weigh down the kite and turn the pump on.
The batteries are not expensive. It pays to have 2 anyway,you charge up the spare for a backup.
Electric pumps are like Cell phones, once you get one,you wonder how you ever did without it !