How can i set a button to display the status of an extension that is on a second server?

You have to configure the server manager credentials in fop2.cfg , see:

http://www.fop2.com/documentation-confi ... ngMultiple

And in buttons.cfg add it like:

[SIP/remotepeer]
type=extension
extension=1234
context=default
server=192.168.x.x
label=remote sip

How can i set a button of an extension on local server to also display status of a DAHDI extension on secon server?

This will happen automatically, but you might have all soft of problems. You cannot monitor same device names on multiserver in a reliable manner. DAHDI/1 on server 1 or server 2 will both impact on the DAHDI/1 button.

Just try it out

[DAHDI/1]
type=trunk
label=trunk
extension=1
context=default