So how about using RPI as a network bridge between the router and the client hosts and then using Ntop, arpwatch etc. Then you can actually monitor the traffic in detail.
Over years I started with a freebsd box with a front wired network to a DSL link that had no other clients physically connected to it, with wireless and wired backend cards in it to serve the client networks... To a system where the freebsd router had a single drop and two interfaces and did routing between them and DHCP'd for the client network (and the physical network was bridged between wireless and wired by the wireless router I had bought)... To a system where I just have a wireless router and don't worry about it that much any more. I get traffic stats, connected clients, etc which is mostly what I need to know about. Its nice being able to sniff all your wireless traffic at the AP, its also nice being able to tcpdump all your transit, but ultimately the complexity wasn't worth the flexibility for me.
However, maybe at least setting up DNS server on Pi would get some "live" stats without sacrificing performance ?