I was playing around with the Opie clock today and I discovered to my dismay that alarm wakeup is not working at all on my iPAQ h2200 running a self-built Angstrom + Opie image (2.6.21-hh17 kernel). It turns out that most of the pieces of the system are working fine up until the point when opiealarm (which gets run just before suspend) tells the kernel to set the rtc wakeup time. According to the rtc info in /sys it is being set to a date somewhere in 2035, which is not particularly useful especially if you really do want to be woken up early for that meeting tomorrow morning.
I have looked at the code in opiealarm and it looks OK to me, and hasn't been changed in a long time. It is using the old ioctl() based method of setting the alarm but that really ought to work properly. I suspect this is a bug in the kernel, but with the handhelds.org kernel discussion mailing list being down I'm not sure where to report it. Setting the wakeup time through /sys does work so at least that's something - if it comes to it I suppose I could modify opiealarm to use that method if it is available.