How to record mouse-pointer fixations?
I think the key term here is dwell time. There is abundant literature on this. For example, Sample et al. (2008), go into quite some detail as to how to calculate this. In a nutshell, it basically boils down to defining a cluster of pixels around the mouse pointer tip. If the mouse cursor stays within those bounds, the clock should start ticking. A certain time-based cutoff criterion (say a few hundred milliseconds) could mark it as a dwell.   

Reference
- Sample et al., Geospatial Services and Applications for the Internet (2008), Springer