PACT is the industry standard brand.
CED is gaining fast because their model 7000 is very small and has a 10 string memory which is convenient for practice. You can shoot the same exercise repeatedly and review for improvement... or consistency.
Competition Electronics timers are also in wide use in the USA. I use one of their chronographs and like it.
You can get a timer app for a smartphone but I would not rely on it for serious use. Maybe something to see how much a real timer would help you.