After many years of not thinking that hangboards where that useful I have just recently become the proud owner of a Beastmaker (http://www.beastmaker.co.uk/
Hann, I also thought that it would only be useful for power and finger strength but it is in fact also a very useful tool for Power Endurance. Ethan Pringle has a very good 20 minute session comprising dead hangs and pull ups all completed on the minute (google it) - the initiation version will leave you completely wasted, and then there is the moderate and difficult (30min) versions after that!
Also being a wooden board I find I can supplement my normal training at walls and rock easily without destroying my finger strength. If you are looking to make your own I would definitely try to use wooden grips as there is nothing worse than the thought of torturing yourself on a rough and sharp hangboard!