It is possible to make application that utilizes the phone, receives and sends SMS. This can in Linux enviroment be done by using AT-commands, as there is currently no Linux version of the Nokia PC Connectivity SDK available for this phone.
I'm doing this right now under Linux using the gammu suite over IrDA with a Nokia 6610 phone. Gnokii has some broken structures and offsets for the 6610 (which seems to be different than the 6210 for which the structures were coded). I posted a report of what was broken and what structures needed updating to Gnokii, but no telling when that will be integrated in. Gammu seems to handle the 6610 just fine over IrDA. I've got a spooler picking up incoming SMS messages and sending messages out. Just search FreshMeat <http://freshmeat.net> for gammu and follow the links.
Right now, thanks to the proprietary DKU-5 cable, you have to either use a third partly clone USB cable based on the Prolific PL2303 USB to serial interface chip for USB or use IrDA. But IrDA sucks, since you have to manually put the phone in IrDA mode and it will drop out after a couple of minutes if it doesn't get polled (mine has been connected to my gammu server now for almost a month). I would prefer to use USB and not be vulnerable to a reboot or outage that loses the IrDA connection and requires manual intervention. Got one of the clone cables on order. The DKU-5 was a waste of good money.