asterisk users - Jul 2005 - NEWBIE Question: Asterisk with multiline/button phones

This is a very newb. question.

Been using asterisk very happily now for several months and am considering
getting some of those really 'cool' multi-button phones with LEDs and
buttons.

It's unclear to me if it is a straightforward task to actually setup a
multiline 'presence' on the phones where the LED's light up when
someone
picks up a 'line' or is using a 'line' or puts a 'line'
on hold or park
and then would like to pick it up from another phone just by pushing
the 'line #3' or 'line #4' button that is on hold and
lit/flashing.

Is this something that Asterisk actually does with ease?
Or is it this a really complicated thing to accomplish & setup?

In particular in a sip only environment... no actual phone PSTN (pots)
'line's involved but with multiple SIP voip accounts to work like
'lines'
with real PSTN phone numbers.

We have several VOIP SIP accounts.

Thanks & take care!

Steve