[c-nsp] Restricting VPN connections to company hardware?

[Scott Granados]

Hi,
    I've been googling but not finding much although I think I'm probably 
formulating my search incorrectly so I'm hoping for some pointers here.
    I use ASA 5520 hardware to provide VPN services to end users with Cisco 
VPN clients and some L2L sessions.  We've been finding that folks are 
configuring IPhones and other non approved devices to attach to the network. 
What's the best method to certify that end users are connecting with 
approved devices only?  Is there a good way say for me to allow company 
provided laptops but not allow clients from home machines where users 
duplicate their profile or non-certified end devices like pocket PC devices? 
I understand how to filter based on client type but this doesn't prevent 
someone from copying their profile file from one machine to another.   Any 
pointers would be appreciated.

Thanks
Scott