That a machine is attempting to replicate this function is an accurate assessment. The machine might remember your previous emotional states, but that is true of a human being as well. As with any machine-based information gathering, it is less the gathering of the information than the subsequent storage and usage of that information that provides the greatest ethical threat. The second is that one's emotions -- or perceived emotions -- are fleeting and therefore not an integral part of one's existence. Outside knowledge of one's emotions is common and there is no precedent for attempting to gather this knowledge being unethical. This is neither an invasion of privacy nor a worthy technology. It is unlikely that this technology would replicate human ability to read emotion in others, because of individual variations and subtleties. In addition, there is little evidence to suggest that a machine can develop the same type of interactions with people based on emotional state that other humans can -- indeed it is unlikely that even an intelligent machine would have the same concept of emotions...

The technology would not likely offer anything useful to business. I would probably avoid an ATM with such capabilities, if for nothing else than the nuisance of it. I do not need it, nor want it, so I would choose to use another machine that is designed more in line with my needs as a customer. There are no particular ethical ramifications to such machines as I do not see any ethical conflict regarding them. The only reason the question is asked is because it is a machine -- the same question has never been asked of human customer service personnel. To me, the machine issue is a non-issue so there remains to ethical issue to consider with respect to emotion-reading machines.
Works Cited:

Goertzel, B. (2004). A general theory of emotion in humans and other intelligences. Goertzel.org. Retrieved February 3, 2011 from http://www.goertzel.org/dynapsyc/2004/Emotions.htm

Tuckness, a. (2010). Locke's political philosophy. Stanford Encyclopedia of Philosophy. Retrieved February 2, 2011 from http://plato.stanford.edu/entries/locke-political/