Several players have a RTC chip, and IIRC all those players already have a RTC alarm that can wake up the player.
This is not true. E.g. the Archos V1 Recorders have an RTC but alarm wake up is usually not possible - it needs a
hardware mod to get it working. As far as I know the Sansas have an RTC but cannot wake up from it. The H300s, X5 and M5 (those have the same PCF chip) have an RTC but cannot wake up from it as of yet; there is a patch in the tracker to make it work but it still needs changes in the Iaudio bootloader to make it work properly. As far as I know this currently only works for the Archos V2/FM recorders and the newer Ipods.
You can then use the "Startup Screen" setting to go directly to the recording screen or FM screen.
Well this would throw you into the recording screen but would not automatically start a recording. If the sound input is already present, triggered recording might help with that.
Also, what happens when the scheduled recording begins? Does the player stops playing whatever it plays, and switches to that FM station?
If the player is started by an alarm there isn't anything running, so that's not that of an issue.
Maybe the question was if it was possible to use the alarm to switch to recording even if the player was "on"? Currently you really need to switch the player off to see the alarm working (and a wake up alarm capable player), I think there was a technical reasons for it but don't know it.
There already was a patch for scheduled recording some time ago which did not use the alarm function but the user timer. This means you had to leave the player running all the time but then it worked on targets with
out RTC too (at least it should have, I never tried). I believe it even was committed but reverted as it caused some problems - unfortunately I don't remember the details. It also caused a quite big binsize increase which means all (with a recording capable target) would have suffered shorter runtime just because of this feature which was only asked for by a few people. It could have been this specific implementation and a better one could be possible without these disadvantages... This patch was discussed in the forums here, you could search bit and find out what happened with it.