Clarification about gtk_main() and running simultaneous non-gtk functions

[Michal Porzuczek <mporzuczek gmail com>]

Correct me if I'm wrong but the gtk_main() acts like an infinite while
loop that waits for callbacks to the widgets that have been created
before gtk_main() was called.

My question is, except for the g_timer function which seems to just be
for measuring proccesses inside actual callbacks, is it possible to
have timers running simultaneously with gtk_main() without calling a
separate program? That is, would it be possible to create a seperate
while(1) that say checks for the value of some variable while
gtk_main() is already running?

Thanks

Michal