Basic Stand-Alone Timer

Hi,
I am very new to this so please bear with me. I am building something for a project at school and I need to measure constant airflow from someones mouth. I need it to have a digital screen and count up in seconds (i don't expect to need more than 3 numbers displayed!). I would like this so that when there is no air pushing against the target it will be turned off because of a weak spring. When someone starts blowing I would like the circuit to complete with the battery, the screen come to life and start timing. As soon as the air is not blowing the timer should turn off and be ready to start at zero again for the next person. Is this possible? If you have any ideas that would be great. Size/apperance doesn't matter.
Thank you,
Ben

Try a microcontroller?

Or you could use a crystal oscillator frequency divider counter and another counter with an LED/LCD display.