Teenagers develop telepathic powers. The first one is teamed up with a ship sent by the Galactic Union. GU is a intergalactic UN. The emergence of the telepaths is the first step for a world being admitted. Tomorrow people are the first step in the evolution of the race. Eventually everyone on a planet is born a Tomorrow Person. (genetic throwbacks exist, but are a rarity).
Main limitation of Tomorrow People, in addition to the fact that the oldest is only about 20, is that they cannot kill. Psychological limitation.
The computer also controls their teleporter/transporter.
It was one BBC channels attempt to counter another BBC channel's Doctor Who. The first season's ridiculously clunky belts are later replaced with much better, more subtle version.