Have you looked at using the support Seam has for timers:
Normally the Timer creates a new thread to execute work - this thread isn't under the control of Seam - so bijection won't work. If you use the Seam support it should work. But this does require EJB
I wasn't aware of Seams support for timers at all... I must have overlooked it. Using EJB is not a problem, so I'll check it out tomorrow, thanks!