I found that it is possible to customize sounds instead of led colour, that is incoming emails have a long sound, WhatsApp messages a short, pitched one and messenger notifications a short, double tuned one. This is in stock DTEK 50. I wonder if those sounds can be customized more, so as to get auditory personalized notifications. An obvious disadvantage is that you can't keep the phone totally silent, this may be a shortcoming in meetings and other common social situations where a buzzing phone may disturb participants