Hi,
This is not a great example as the code has 'evolved' rather than follow a plan but it does update an LCD Every second, respond to new lap times instantly, plays an audio count down while responding to laps and updating the LCD, operates in a menu, lap review or recording mode etc. It does so through the two mechanisms already mentioned - interrupts for laps and time/timestamps for screen and audio updates.
PM Me your email address for a zip file of the code - like I say its not text book perfect but is an example of a very usable project that has been rapidly built/evolved on Arduino -
Duane B