I have a network whose broadcast address is 192.168.2.128

yikes. well... actually, assuming that jemplode can figure out the correct subnet mask, if your mask is 255.255.255.128, it should catch it, if i recall my CCNA readings. but if there isn't, jemplode might as well port some nmap routines to quickly syn ping the whole subnet. i also was reading something on /. few months back about "black ops in tcp/ip" where they wrote a program to find which ips had port 80 open... yeah, nothing new except they got the results of 65000 ips in 3 seconds.