Is there a service out there, or is there any intention to integrate Standing Order type transactions into the client ? (Every 30 days transfer 0.2BTC to a specific address for example).
One way to accomplish this today is to run Bitcoin with the -server switch. Then, create a cron job (Linux) or scheduled task (Windows) that calls bitcoind with the proper arguments. Something like...
bitcoind sendtoaddress <address> <amount> <comment>
The up side of this method is that you can run a lot of different commands this way. See the wiki for a full list of available RPC calls.
I don't think the client could be relied on for this as it would need to be running all the time.
So you would need a 3rd party e-wallet service.
Technically this would be very easy to do.