On Wed, 27 Oct 2004 12:51:37 -0400 (EDT), Seth Rothenberg
<seth at pachai dot net> wrote:
> 
> I am thinking that any *IX system on the internet can be told
> that my m0n0 has a route to the WLAN on the other side...
> eg, I can just do
> route add 10.mmm.nnn.0 [gw]  64.xx.yy.zz      (use gw if OS=Linux)
> 
> I would then need to allow ICMP traffic to route
> between 64.xx.yy.zz and 10.mmm.nnn.0 -
> 

No because private IP's are just that, private, and non-routeable. 
You could set up a VPN tunnel and ping the private IP.  Or you could
set up a firewall rule to permit your remote system to ping the WAN IP
of m0n0 (if that'd accomplish what you're wanting).

-Chris