I'm not limiting myself to bluetooth.
I can use AIM as long as I am in a wi-fi environment. So, when dad and I are visiting mom in the nursing home, I can type in my computer, and he can see the message on the Touch because the nursing home is a wi-fi environment. When I'm at my dad's house, there is no wi-fi, so I need to use bluetooth. There are bluetooth apps, but, the bluetooth apps are for iTouch to iTouch, not for laptop to iTouch. So, there is no bluetooth app for laptop to iTouch, and so when I'm at dad's home, I just have to shout or repeat myself until he understands. The other thing I do is use the computer and just show him the screen, which is fine if we are sitting at a table together, but if he's in an easy chair and I'm across the room, that's tougher.
I use wi-fi whenever I can. I need a bluetooth laptop to iTouch app for times when wi-fi is not available.
I just don't see why you can't do this on a regular online messenger. You simply create a screenname for your dad (takes less than 2 minutes). And you can use AIM (or other 3rd party ones) and get the same result. Also, WiFi has a greater range than BlueTooth, so you shouldn't limit yourself to BlueTooth.
But as someone already posted, there are BlueTooth Chat apps in the app store. Those are nice as they don't require a screenname/signup process but then again, a one-time 2 minute process isn't difficult.