I read a short piece at New Scientist about a research project at IBM called Mercury, which helps switching from one medium, like voice over POTS, to another, such as IM.

Mercury "will track where you are at work, at home, in the street and plug you into the medium you prefer in that location, whether it be cellphone, email, instant messaging, pager or landline phone.

Mercury can also be made "context aware", by detecting whether a laptop is running a presentation, for example. You could then set it to refrain from sending a message that would interrupt a business presentation, but allow it through if a game is being played."