OK - i have looked and looked over the countless posts regarding Security Systems and Vera with Z-Wave and i’m more confused now than when I started so please keep the ridicule to a minimum - i’m sensitive 
I purchased a Vera 3. ;D
I have added 8 z-wve window/door sensors
4 z-wave Light Switches (dimmable)
3 Kwickset Locks with z-wave
I love this system - scenes and all.
HOWEVER…I have since learned through this forum that Home automation (micasaverde/vera 3) is not the same as a tried and true security system.
So now I need a wireless security system (that I would like to integrate with my z-wave devices)
I have seen that the DSC powerseries panels are compatible and they have some new thing called connect C24
I have seen some Ademco Vista discussions
I have even seen reference to 2-gig
Then there is discussion about IT-100, EnvisaLink 3, and other interfaces as well as ‘plug-ins’
Although this is all simple and commonplace discussion to the majority of you technological genius’s, my brain hurts :
Here is where I need (the most) help…
I would like to purchase a ‘wireless’ security system (older home and do not want to run wires) - open to suggestions 
I may eventually opt for remote monitoring - for now, I’d like to use Vera 3 :-\
I have invested in several door/window z-wave devices already - can these existing z-wave devices be used for the new alarms system instead of purchasing new ones for what ever alarm system I buy? ???
This is a good base DSC system that supports up to 32 wired or wireless zones:
You’ll also want a EVL3 (sucsessor to the 2DS) to interface it with:
You can use your other Z-wave sensors for other tasks with Vera, but as far interfacing with the Alarm, they wont really help you. If you have 8 then sell them, since for every one, you could likely buy a couple of wireless alarm ones that are not only much smaller (or even concealed in a frame/Door), but with far better reliability and battery life!
I’m not sure but don’t think you can learn any z-wave device into more than one system. Also (and I could be wrong) I don’t believe any security system uses z-wave for wireless contacts, only home automation. each manufacturer has their own wireless protocols and only their devices comply with it. I have been able to mix devices and panels with an interface from the panels manufacturer but the only z-wave contacts I have come across have been for automation purposes like status or scene control. But you are correct in thinking that the Vera should not be your only source of security. It’s only as secure as your wireless network. I have three separate systems at my house Vera 3,Dmp xt50 and a 16 ch Speco Ls dvr and though all of these systems are linked together in someway if one goes down or has been compromised I the other two will still report my alarm condition hopefully I’ve been able to give some insight. Also nothing is impossible you can make your Vera report to a central station with the addition of a regular alarm system just add some motions to it ( for stand alone security if needed)and let Vera handle the doors and report them to the alarm system via contact closure and some creative scene scripting though the likely hood of false alarms is fairly high