The campus board must rank as the most efficient workout form possible when it comes to developing upper body strength. A 10-minute workout on the board will feel like an hour in the gym the following morning. For those unfamiliar with the device, it's an angled board suspended about six feet above ground with nine horizontal rungs, about an inch and a half wide, about 10-12 inches apart. A number of different exercises are possible, the most basic being pulling up from one rung to the next, like climbing (the back of) a ladder without using your feet, first up and then back down again. The next step is to start missing rungs out, for example the 1-3-5: from rung 1, pull up to rung 3 with one hand, and then to rung 5 with the next. Taken to its logical extreme, we get the 1-5-9, a digit combination that has a near mythical meaning to climbers. But the real win on the board is to move from rung to rung with both hands simultaneously, especially if this is done both on the way up and down again. This is considered to be the most efficient recruitment training known. Recruitment is one component of the strength/power equation, the number of muscle fibres that the brain and nervous system can recruit to do the work. The higher recruitment, the more 'explosive' your muscles are. Power is strength developed per time unit, so to increase your power you can either increase your strength, or decrease the time it takes for your body to 'switch it on'. The campus board can work both aspects.
The device was invented by German superstar climber Wolfgang Gullich as a specific training method for the preparation of the route Action Directe, the world's first grade F9a in the Frankenjura. It's basically a big campus board, involving 6-foot footless spans between single-digit pockets. When he started out he couldn't even hang the mono pockets, let alone move between them.
As a training device, the campus board has quite a high barrier of entry - few people can do the first joint pull ups that's needed even for the most basic laddering. There are ways around this by for example starting out supported by a bungy cord or by using one foot initially to take some of the load. More seriously, due to the intensity of the training, it's very easy to get injured, especially in elbows and shoulders.
Be good, and if you can't be good, be strong.