is it possible to write ACL iRule for specified cell phone

as mentioned in my post, and in the same way aaron wrote,

 

don't use the "user-agent" for your ACL.

 

Use it to identify the cell-phones to direct them to special servers (where you can put smaller files and images), and if you need to identify the users, use something like client certificates or client authentication (ACA module on LTM), to force their authentication (and their "identification, of course ;-) )