SpeedStacks is the original company that was the leader across the world in Sport Stacking. Sport Stacking is a sport in which competitors compete to stack cups in certain arrangements in the shortest time. SpeedStacks manufactured the cups, timers, as well as the mats for this purpose.
Needless to say, speedcubing, being so close in concept to cup stacking, caught on with the same timers and mats, and hence, SpeedStacks gear became the most commonly used and widely accepted officially too.
The latest timer is the G5 timer, but the most used one is the G4 timer. The G4 mats (available in two different sizes/designs) are the most compatible as well. They also designed a small bag in which one can store the timer+mat together or even other cubes.