Its natural to ask that given this importance, how can these context aware systems be useful.

Well, before we answer that question we have to define what “context” is

We like to define context by breaking it down into 4 parts (Who, What, Where, When)

Who: This is your identity and relates to your gender, age, weight, height, background, profession etc
What: This looks at what your current activity, ambience or interests are.
Where: This is your location (not just a lat, long) but also what type of taxonomy can we attach to that location for e.g. home, office, commercial, residential, restaurant, etc and also add more attributes around that location.
When: This tells you what time of the day, week, month, year etc is relevant to the current context.

So, given this definition of context we can define that a context can be used (i.e. personalised) as follows

WHEN a WHO is doing WHAT at WHERE then do ACTION

The use cases can then be derived as following