I present to you a challenge... at least for me anyway...
  
 Imagine you have a cellular router connected to an L3 switch, and 2 devices behind it at one location.
  
 You have a different piece of hardware connected to the internet in another location with a LAN port specifically designed as a sniffer.
  
 How would you get these two networks to talk and be able to sniff traffic across a VPN or similar using the (remote) LAN port on the sniffer?
 
Would I need a VPN concentrator on the sniffer's end to consolidate the traffic if using multiple cell routers/VPN connections?
 
See the pathetic excuse for a network diagram below.
 
I appreciate any advice or tips you guys could offer.
 
Cheers,