New trigger inputs for the ALICE Central Trigger Processor (CTP) are proposed. They are based on the use of Fast Multiplicity (FM) output signals generated by the ALICE Silicon Pixel Detector (SPD). These can be used for a multiplicity based centrality trigger and for a fast on-line computation of the primary vertex. A simple algorithm for primary vertex location at the trigger level is proposed. The precision that can be achieved with this method on centrality selection and primary vertex location, is discussed for interactions with different pseudo-rapidity density level. The feasibility of background rejection is also considered
