ActiveHomePro just purchased it?
Hope you went for the full package at 49.99 which includes OnAlert security module.I use it with DS10A&MS10A and it works great.
By the way if the range is not enough with CM15A may I suggest antenna mods -some really great ones out there.
If you need any help please feel free to post it in the appropriate section and/or email me.
As for the CM19A it is a RF transceiver USB powered and works with X-Ray vision soft(free) and Firecracker(also free).
If you have a second PC you can use it to turn lights or react to motion sensors.
You're CM15A should be within range or to avoid repeated commands use it for certain housecodes not transceived by CM15A with a TM751.
You may also simply keep as a backup in case CM15A goes on the fritz.
It is included in package and you can even control cams with it.Uses are endless restricted only by the user.
The best bet is look around the forum by searching CM19A terms.
The oldtimers have some great ideas either relating to CM19A or X-10 in general.
I can honestly tell you by looking around it saved me headaches and aggravation as well teaching me some neat tricks.
Spend a whole lot of time on this forum before spending money on X-10 to make sure you get what you need.
Hurts less to read than spending money and realizing it does not do what you expected or not what you needed at all.
[TTA Edit: Combined 2 sequential posts into 1 via MODIFY. ]