Several credit card issuers and banks offer accident covers along with the cards. Again, the company buys a group cover for the purpose and no premium is to be paid by the user for the cover. Their structure and claim process are mostly similar to a regular personal accident policy from a nonlife insurer. In the event of the holder's death, a lump sum is paid out to the nominee. Such covers could come with permanent disability riders, too, to provide succour to the insured if s/he meets with a debilitating mishap.
They may not cover loss of wages in case the policyholder is temporarily incapacitated and is not able to resume work. Also, there is a possibility of you becoming dependent on the bank or the issuer merely because of the cover. You would do well to consider buying a basic cover, independent of such products.
To sum up, ensure that you focus on the merits of the main product. If it fits into your financial plan and serves your purpose, go for it. Any additional benefit would be a bonus.