See also:
Chen, M. C., Anderson, J. R., & Sohn, M. H. (2001, March). What can a mouse cursor tell us more?: correlation of eye/mouse movements on web browsing. In CHI'01 extended abstracts on Human factors in computing systems (pp. 281-282). ACM. (See attached)
Kim, N. W., Bylinskii, Z., Borkin, M. A., Gajos, K. Z., Oliva, A., Durand, F., & Pfister, H. (2017). BubbleView: an interface for crowdsourcing image importance maps and tracking visual attention. ACM Transactions on Computer-Human Interaction (TOCHI), 24(5), 36. https://arxiv.org/pdf/1702.05150
I don't know how readily available mouse-based attention tracking solutions are. But from the literature, it seems like there are good options for understanding attention through purely software means.
-Aaron