In addition to his popular science and maths books, which include books on Isaac Newton (Dead Famous: Isaac Newton and his Apple), puzzles, practical jokes and secret codes, Poskitt has written a book of magical tricks, a GCSE Maths support book and four Rosie and Jim annuals. In 2007, Poskitt published the first in a new series of children's novels called Urgum the Axeman.
He also wrote the theme tune for the children's art program SMart, as well as the title theme and music for the first two series of Brum. He is also the creator of a logic puzzle, Kjarposko.
He has been a presenter for a number of (mostly BBC) educational children's TV shows.