at last, i can say it.....
yes it's trivial.
it's very easy to output a square wave from a pic with full control over frequency and duty cycle... you just toggle the pin value when required by a preset delay. i used a spare 16f84 to do just this while debugging a zero cross iinterrupt routine on a 16f876a controlled dimmer.
of course a 555 is easy too, but you have to hang more bits and bobs off it to get the same result [assuming you have a pic programmer].
if you've got a spare low end pic my choice would be to use that.