There are a lot of stopwatches out there, they all fundamentally do the same thing but there are subtle and important differences.
For example some stopwatches only run on certain devices, this is the case with most apps. A stopwatch app that was created for the iPhone for example will not work on an Android phone.
Then you have online 'apps' like this stopwatch that uses standard web technolgies like HTML and JavaScript which function on almost anything with an Internet connection.
But just because it's a website doesn't mean it will work on any device. For example if a website uses Flash it will not work on the iPhone or iPad. Websites that use Java might have similiar problems.
Of the websites that do stick with HTML and JavaScript you have to find the one that's right for you. Some stopwatches have a 'split' feature that let's you record particular points in time. Others like this one has the feature where it will automatically resize to utilize your whole monitor, making it ideal for large audiences.
Check out some of our special count down clocks: