There is an SMB monitor for LTM. You can see it in the LTM monitors section of the GUI when you click create. In looking at past cases, it seems that there might be a problem with it though.
If you have any problems testing the inbuilt monitor, I'll upload a SMB/CIFS external monitor script to the monitoring codeshare today. I have a customer who needs this for GTM. I'll reply with a link once I'm done testing it.