daily task

I need to achieve something similar, and my initial approach was going
to be to have a cron job that called the relevant rake task on a
regular basis.

My ideal approach would be to have some form of daemon that waits for
data to arrive and then processes it, but at the moment the cron
solution is much more achievable.

You both can either use a cron job (set a script/runner or RAKE
<Somthing> line in crontab -e), or either using BackgroundRB. BRB is a
bit heavy, but both works just fine.