Lift idea - revisited

I think the success of this project will be gauged on the messages put across and the positioning of them. You've got those that are directed squarely at the user - "Hey lazy, go and use the stairs" etc. and those that seem as though it's the lift communicating with the user as if it were a person - "Stop walking all over me," "Hey, go away, I'm trying to sleep here". Two distinct ideas that could be merged under one 'umbrella'.

Considered the possibility of audio feedback. Will the lift speak the message as well as project it to the user? Will there be a 'ding' when the user walks into the sensor area? Might be best to have the sensor as a magnetic strip or something on the roof facing downwards to detect anything that passes by to turn on the projected message.

There is the possibility of extending this idea further - have a sign at the top of the stairs saying "Congratulations on not using the lift. Have yourself a stick of celery as a reward" (of course, this is supposed promote healthier living). Have the two being used in conjunction with each other and the lift's mood changes as people use the exhibit. If someone uses the stairs (a separate sensor for this) then it would become happier whilst if you use the lift it gets angrier. The comments displayed would reflect this, starting off as 'Hello there. Have a nice day!' and progress to grumpier things like 'Get lost I'm having a sleep here'. Maybe it would display happy messages if someone uses the stairs but angry ones if they don't.