This may help...
If you have your own iOS5 device, such as an iPhone, iPad, or iPod Touch, you can set up iMessage on your own device and have configured it to monitor any conversations.
On your own device, enter "Settings>Messages>Recieve At". Add the email address that is registered to your daughter's iPod in addition to (or instead of) any existing accounts you use for your own messaging. Once verified, any messages sent to your Daughter's address using the iMessage protocol will be delvered to both devices simultanously, allowing you to monitor the conversations without physically possessing the iPod Touch.
Note #1: This method is not effective to monitor iMessage activity on another iPhone. It can be done, but you will only be able to view iMessages that are sent to the users email address (NOT the SMS phone number). Most people will use the phone number as default; since iMessage automatically changes the protocol once it recognizes that both the sender and recipient are using iOS5, there is no need for the sender to use the email address format. Since your Daughter's iPod is not capable of using the SMS protocol, this will not be an issue for you, but I thought I'd mention it for anyone else referrencing this post...
Note #2: I use this method to monitor both of my Daughter's devices for unsolicited messages (with their knowledge, as they are both under 12). I found it to work flawlessly when only one of their accounts was set up on my iPad, however having both of their iMessage accounts intermittently seems to lock out one or the other. I imagine there's just a configuration workaround, but I haven't had the time to tinker with it quite yet.
Hope this helps!
@ianmccamey - So true! Our parents never had to worry about this kind of stuff! 8-)