Yes, it's happening, but inexpensive tools aren't widely available or integrated into a lot of content, and content isn't yet being widely developed with dynamic content in mind. There needs to be work in how 'teachers customize instruction' that challenge widely used instructional design models.

There's a lot of work being done in places were the pockets are deeper (military, simulations, medicine). Recently, standards (xAPI, Caliper) have started to emerge to enable the decoupling of content, content delivery, and interaction (think MVC pattern) and to enable pervasive, multi-modal learning activity tracking.