Watchpoints are evaluated expressions that makes the '!contwp' command stop stepping when they match. You can setup multiple expressions and logical operations and groupping checking for memory or register values.
e cmd.wp = pd 3 @ eip
e dbg.wptrace = false
The 'dbg.wptrace' is used to make the watchpoints stop or not the execution when a watchpoint expression matches. The 'cmd.wp' will be executed every time a watchpoint is matched.
[0xB7F45A60]> !wp %eip = 0xB7F45A8B
0: %eip = 0xB7F45A8B
[0xB7F45A60]> !contwp
watchpoint 0 matches at 0xb7f45a8b
[0xB7F45A60]> pd 1 @ 0xB7F45A8B
0xB7F45A8B eip: 01d0 eax += edx
[0xB7F45A60]> !wp %eax = 0x6fffffff
1: %eax = 0x6fffffff
[0xB7F45A60]> !contwp
watchpoint 1 matches at 0xb7f45abe
[0xB7F45A60]> pd 1 @ 0xb7f45abe
| 0xB7F45ABE eip: 29d0 eax -= edx
[0xB7F45A60]> !reg eax
0x6fffffff
[0xB7F45A60]>