Assuming you already have the MAC addresses of the host(s) you want to
wake, you don't need
nmap at all. There are two packages available on RPi that will send the required WoL "magic packet" to the host(s) you choose:
etherwake is one, and the other one has the unlikely name of
Which one is best? My preference is
wakeonlan because it doesn't require
root privileges to run (no
sudo required). You may install them both, and determine your own preferences:
$ apt-cache search etherwake
etherwake - tool to send magic Wake-on-LAN packets
wakeonlan - Sends 'magic packets' to wake-on-LAN enabled ethernet adapters
$ sudo apt-get update
$ sudo apt-get install etherwake wakeonlan
And now you're ready!
man etherwake and
man wakeonlan will fill you in on the details for using either of these packages.
As you already know, the host(s) to be awakened will need to have the "Wake-on-LAN" feature enabled. If they happen to be Raspberry Pi devices (or "adult-sized" Debian hosts), there's a good tutorial/how-to that covers that in the Debian wiki.