Life exchange
A life exchange is like a stock exchange in that buying 'shares' in it is accepting some risk to some life, that you consider worth paying to protect - just as shareholders accept some risk to money when they buy into a company.
Shares and options and futures and other instruments can be created to mirror the various risks to life that campaigns are trying to protect. To buy in to a campaign, you can either buy a share in the campaign (which is a bet that the campaign will increase the value of the life affected by the activity that the campaign targets, which you consider worth doing for itself - like a tradeable donation) or in some derivative of the campaign (like a fixed deadline at which point the success of the campaign in raising the value of some life will be assessed and you will be paid some premium for predicting that rise). A combination of the two approaches makes donations and bets on the success of the campaign work together more closely, and provides accurate feedback on probability of success: betters don't care if the campaign succeeds so their bets tell you objectively what the odds are to see if you are impressing or scaring anyone with the campaign; shareholders do care if the campaign succeeds because they get prestige and possibly a payoff of some kind out of it.
So, betting on/against campaigns reveals price of life, buying shares in them increases price of life that the campaign is pointing out the bad effects to.
But what does it mean to accept a risk to life, or increase the value of life? These concepts are used in insurance and economics all the time and are not even controversial. When you buy an insurance policy, for instance, that means an insurance company has accepted some risk to your quality of life or duration of life. If you get hurt or die, the value of your loved ones in the economy goes down, because they do not have access to your labour or love any more - they have to buy things to replace it - therefore they get paid something. The insurance company has kept their value and quality of life higher than it would be.
Price of life is more difficult to explain, but it comes from the fact that many decisions are based on budgets and limits. There is not infinite money to pay for ambulances, road safety, crime prevention, medical research, bridge building, so, at some point a decision is made that "5 minutes ambulance response time is enough" or "20 tons of bridge gross tonnage is enough" or "10% of doctors' time spent on medical ethics training is enough". That means that the person who lives in 4 minutes but dies in 5, who drives the 21-ton truck over the bridge, and would have been saved if the doctor had spent 11% of his or her time learning not to deal out drugs that the drug company suggested, now are dead. Their life was valued deliberately lower so that others could be saved by spending the time or money somewhere else.
There is a lot of research on how these prices are set on individuals, whole ecologies (like the rainforest), the whole planet (one study by w:Robert Costanza showed that the Earth provided 1995$US33Trillion in services to humans every year, thus it must have a value in the quadrillions of dollars), and how changing certain decisions changes that price of life for everyone. But this price is never the same worldwide. The International Panel on Climate Change calculated that in the developing world a human life was worth only 1/15 in cash what it was worth in the developed world - this was used to calculate numbers in the Kyoto Protocol. So there is official sanctions on how to do this calculation in some circumstances.
But even if you think globally you must act locally. When you buy tuna in the grocery store, if you will pay even an extra penny for tuna that is "dolphin - safe" then you have raised the price of a dolphin life by quite a bit. It becomes more profitable to go dolphin-safe and charge you that extra penny, than to kill dolphins and charge you a penny less. Life exchanges would let you bet that the price of dolphin life is going up not down, and profit from that. If a lot of people bet that it is staying the same or going down, then, that will be noticed by campaigners. Then they can start a campaign to raise it, and those who bet it will stay down (while there was no campaign) can shift bets into the shares the campaign, which is a bet on its success, and contributes to success.
The same logic lets you buy an acre of rainforest, or give money to educate a child, both of these increase the price the economy puts on that life halfway across the world.
Some economists think that commodities and products are both bad ideas, that everything is services, and that all exchanges will be life exchanges in the future. In this world, you will basically bet obstacles out of your way that prevent you from having the quality of life you want for yourself and life that you care about. You will bet that the money you made by giving up some time of your life, can create more than that much time in the life of those you care about. The movie w:Pay It Forward was about exactly this kind of idea, and is highly recommended for those who want to deeply understand life exchange.