George Hurst is the Father of the hydraulic rescue tool. The "Jaws of Life" is a trademark name for the tools he founded. He came up with the idea as larescue points out, for use in motor sports. The first set of tools put in service was used at the Indianapolis 500 and was so big it had to be carried on the back of a tow truck.
Hurst employed an engineer named F.M. (Mike) Brick to further develop the tool and make it more user friendly. While Hurst is the Father of the hydraulic tool itself, you could call Brick the Father of the modern hydraulic rescue tool. It was through Brick's work that the tool was scaled down to the 60 pound version most of us are familiar with.
Brick and Hurst had a parting of the ways when Brick wanted to further the development of the tools and Hurst did not want to fund these efforts. Because of this, Brick set out on his own and started the Phoenix Rescue Tool line. Those who have used both, will notice a lot of similarity because of this. Brick's improvements were the fixed-blade Continuous Cut (C/C) cutter, a light weight (35 pound)combinations "Rescue Tool" with field replaceable cutting blades on the spreader, exposed links to improve pivot points on the tools and the use of ethyl glycol as the primary hydraulic fluid for the tools.
That being said, what brand does your department use, and how do you like them?