Oh, I see what you meant.

OK, an idea is to have the internal clock set at HFINTOSC=8MHz, then prescaller at 1MHz. So the system clock will be 1MHz/4= 250KHz.

Feed that clock to the Timer1 with a prescaller of 8. So the Timer1 will roll-over every 2 seconds.

With the timer1 you may check the green LED for the time it stays ON and OFF and conclude if the GoPro is recording or not.

Hope this helps.
Ioannis