Any topic of societal interest is worth considering. I feel IoT should make a big way in transportation sector. In Railways, Road ways and other modes of conveyance so that the accidents and disasters could be avoided.
If you want to connect IoT with applications, the areas of Smart Home, Smart Grid, Smart Health, Smart Cities, Agriculture and Public Safety issues are hot topics.
IoT is really very very generic nowadays and some researchers and developers are confounding it with something like "internet of everything", what is "fashion" but not good.
The standards must be our anchors (like Recommendation ITU-T Y.2060. Overview of the Internet of things. ITU-T – International Telecommunication Union, 2012.)