Hi Joerg,
The feature you need DSS/BLF is available in CCM 5.x (and later). Unfotunately, not in any earlier versions of CCM. So you have the either/or choice that you have seen. Either configure the Button as a Shared Line (to see the status) or as a Speeddial for quick Transfers :(
In CCM 5.x this is a traditional BLF (Busy Lamp Field) which is used to monitor On/Off Hook, Busy/Idle conditions on users phones, as well as having a Speeddial functionality for fast dialing and Transfers.These keys can't be used to answer actual calls.
Cisco Unified CallManager Speed Dial Presence
Cisco Unified CallManager supports the ability for a speed dial to have presence capabilities via a busy lamp field (BLF) speed dial. BLF speed dials work as both a speed dial and a presence indicator.Only the system administrator can configure a BLF speed dial; a system user is not allowed to configure a BLF speed dial.
States are:
Idle
Busy
Unknown
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_implementation_design_guide_chapter09186a008070bc02.html#wp1070507
This differs from the "Old" Shared line appearance setups in the CCM 3.X and 4.X trains.
Hope this helps!
Rob
