slave component hosts parameters

[Satyanarayana Jampa]

I have written a custom service component[slave]
How can I get the lists of selected hosts in the "Assign slaves and clients" 
screen to "Customize Services" screen. I want the list of hosts value to be set 
to one of the property in the "Customize services" screen. Or is there any 
parameter which I can use in my service component config.xml file something like
below:
                <property>
                  <name>MY_PARAM1</name>
                  <value>{HOSTS}</value>
                </property>

Also, for master components, why do we see the host parameter as 
COMPONENT_NAME_HOSTS instead of "COMPONENT_NAME_HOST" [without 'S']

Thanks,
Satya.