I saw this PHP Class posted here
http://www.phpclasses.org/browse/package/3787.htmlAnd I thought maybe it would be an idea for working around the cronjob issue. Cronjobs aren't always user friendly and something internally based might be the trick.
Currently I'm a bit busy with the SMFBot project so I really don't have the time to check the feasibility to convert this class into an SMFShop Mod. But I figure someone might be willing to take a look at it.