In recent years there have been several devotees who have needed expensive medical care due to accident or illness which would have been covered by this type of insurance. The US State Department highly recommends travelers to obtain this type of insurance, which includes coverage for air ambulance back to their home country, regardless of their foreign destination.
There are different sources for Travel Insurance cover. Your travel agent can give you the details of the plan they offer. If you have a membership to an Auto Club (AAA, CAA, AA) you may find a cheap rate with them. In the UK the supermarket chain ASDA offers discounted Travel Insurance. AThe coverage includes emergency medical expense coverage, personal accident insurance, trip cancellation coverage, loss of money, loss of passport, loss of luggage, theft, personal liability, and legal expenses. Here is a link to a site that compares travel insurance plans.
This type of coverage also comes in two categories, one where you are reimbursed, and one where the insurance pays immediately. In the case of an unexpected major hospitalisation, you may have to pay quite a lot up front with the former type of coverage.
Though I've never had this type of coverage, I can definitely see the value in it for covering health emergencies which your normal health insurance will probably not cover, and would recommend it. That said, most tickets to India can be changed to another date in case you are too ill to return on the scheduled date though it will require a letter from a doctor for the airline to waive the change fee. Also, the liability coverage is not really applicable to India (you won't be driving a car, and won't need liability insurance).
The cost varies. There are also multi-trip policies. I was quoted £33 for a single one month trip, £55 for one person, full year multi trip coverage.