Just the term double indemnity sounds mystifying, intriguing, corrupt, dangerous, and somewhat shady; but basically double indemnity simply means that for certain approved life insurance policies, that the beneficiary will receive double the insurance amount of that policy, typically for a death that is purely accidental and always subject to the review of the actual issuer of said policy. As you might imagine, life insurance companies are not in the charity business, so if they do indeed offer some sort of double indemnity policy, rest assured, that they have done their research and such policies issued in aggregate will be profitable for them. Also, normally to be even eligible for double indemnity often means the payment of a premium for that optional extra indemnity coverage. Whether there should even be double indemnity clauses issued in the first place, or triple indemnity, or bonus indemnity, or multiple indemnity, or accidental indemnity, is something best left up to the marketplace, but the overall effect is to somewhat tarnish the image of the life insurance business in itself, but it is what it is.
The more intriguing part of life insurance policies, is whether anyone can take out any policy at anytime for any reason on anyone. The answer to that question is no; life insurance companies will only allow people that have an "insurable interest" in the person involved, to take out insurance on that person. So even though you might have a premonition that some certain person is going to die, really soon, there isn't any way that you can profit from that precognition, unless you are the spouse, or perhaps the business partner, or perhaps the domestic partner, or perhaps a very close relative. In any event, to assure that you have an "insurable interest" you must be able to demonstrate that you have a financial need or dependence on the person that you wished to take out the life insurance policy on; which is the most basic reason why life insurance is offered to being with, as should that vital person die, you are counting on that life insurance policy to help make financial things whole.
Another thing that people are inquisitive about is whether you can take out a "secret" policy on a spouse or somebody else that you are financially dependent upon. Not too surprisingly, since you are talking about collecting monetary benefits upon a particular person's death, the life insurance company has a vested and fiduciary interest in actually knowing the person who is going to be insured, so then they will definitely want family health background information on that person, as well as to subject that person to medical testing, so the chances of a "secret" policy being issued on a particular person, are pretty much unheard of.
You can also take out a life insurance policy on yourself, to which this is somewhat typically done for single parents, as a lifeline for their children, should something tragically happen to the parent. In America, there are all sorts of life insurance products for sale, such as term life, whole life, universal life, variable life, and even those with double indemnity clauses; rest assured that although you might think or believe that the insurance companies selling or promoting these policies have your best interests in mind, they are really about the making of that dollar, and monetizing well on your fears and vulnerabilities.