A feature I always liked was one I have seen in some Verizon Wireless markets, but not all -- I know Northern VA/DC/MD area has the following. When you call the vzw number and the called cell line is on a call, I would hear the ring back tone, along with a short beep at the very end of the ring back tone. This signified that the cell line was currently on a call. I really like that feature -- would love to have that for my Voipo line, e.g. when I call home and hear the distint ringback tone that tells me someone is on the phone.

-bird