Is there a tool for showing trend in a technical research field? Does anyone know if there exists a tool to generate the trend of interest in a particular research field over time?

I am particularly interested in wearable computing. I know this field has been hot for the last few years, I would like a measure of this “hotness” using academic publications relating to this area. i.e. the number of publications related to the keyword Wearable Computing.

Is there a tool that shows the trend of publications in an particular topic similar to how Google keeps track of keywords that people searches for?



Note: I am specifically interested in technical research field, such that papers that would get published in IEEE or some computer science journals.
I use Scopus quite a lot and it provides the ability to analyze keywords (there is a link to 'Analyze search results'):


I was able to quickly obtain this plot for publications per year for the keyword 'wearable computing':



It can also be restricted to particular sources. For example
this one for 'wearable computing' in 'IEEE Pervasive computing':



Unfortunately you need a subscription to access Scopus.