IPExpert, it's 2012.

After reading excellent sample chapter from IPExpert's "IPv4/IPv6 Multicast Operation and Troubleshooting" book I decided to pre-order it. Today I got the pdf file and was very disappointed. The content is still great, but it can only be read on the PC or MAC - no iPad, Kindle or smartphone. Now, my commute is relatively long and I do most of my reading on the bus. Not be able to read documentation on mobile device is major problem for me. If greedy Hollywood studios found a way to provide their content on mobile platforms, so should IPExpert. Especially given the fact that INE provide PDF files DRM-free. This was my first and last purchase of IPExpert product.
Update: FileOpen released iPad/iPhone app, so now I can read that PDF on my iPad.

ip accounting-list

Cisco has interface level command "ip accounting" which records number of bytes and packets passed through the router. If you want to count traffic only for specific IP address, you need to use "ip accounting-list" command. There seems to be a tiny bug in context help in 12.4(15)T14:

R2(config)#ip accounting-list 1.1.1.1 ?
  A.B.C.D  IP address mask

Note that context help says you need to enter address mask. 

R2(config)#ip accounting-list 1.1.1.1 255.255.255.255

After checking

R2(config)#do sho run | i accounting

ip accounting-list 0.0.0.0 255.255.255.255

That's not what I entered. In reality, you are supposed to enter wildcard mask, which makes more sense. Specifying ACL number or name would have made even more sense. So, let's fix it:

R2(config)#no ip accounting-list 0.0.0.0 255.255.255.255

R2(config)#ip accounting-list 1.1.1.1 0.0.0.0

R2(config)#interface fa 0/0

R2(config-if)#ip accounting

and test it. Traffic from R3 to 192.168.12.1 and 1.1.1.1 must pass through R2's Fa0/0 interface: 

R3#ping 192.168.12.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.12.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 28/58/120 ms

R3#ping 1.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/47/88 ms

R2#sho ip account

   Source           Destination              Packets               Bytes

 192.168.23.3     1.1.1.1                          5                 500

As you can see from the output above, only pings to 1.1.1.1 got counted.