The invention is for a waterproof Inhaler Usage Indicator with or without a replaceable battery (6), to provide a count of the amount of drug remaining inside the canister (4) with the counter (1) still attached to the canister (4). It is not limited to inhalers alone, but any type of canister (4) that dispenses through a nozzle (24) when placed inside an housing (2) in order to count the number of displacements between the canister (4) and housing (2). The status of the drug can be checked at any time by a quick movement of the inhaler in any axis to allow the motion sensor (40, 41) to initiate the display of the amount of remaining drug uses. The counter assembly (1) is attached to the top of the canister (4) and uses the displacement between the canister (4) and housing (2) to count the number of uses.