There is a Spanish company called Life Length that claims to be able to conduct a test that will tell you how long you have to live. It measures the lengths of your telomeres, which are the end caps on your chromosomes that get shorter each time the cell divides until they disappear and the cell can divide no more. By measuring the ratio of short telomeres to the average telomere length, Life Length claim to be able to estimate how much time you have left. I am unable to give you more detail of how they work their wonders because their web site is so incompetently built that clicking a link just returns you to the links page, but should you wish to avail yourself of their service you will have to part with the trifling sum of €550.
Chromosomes (grey) with telomeres (white)
But why would you do that? The lengths of your telomeres cannot predict that you won’t die of heart disease, say, or economy class syndrome, or being hit on the head by a meteorite traveling at 12,000m/s, or even a bus moving at 20m/s. The main problem I have with this test is that it ignores all other factors that will play a part in determining when you are going to die. You can have telomeres the length of the great wall of China and it won’t deflect the executioner’s bullet, axe or needle one iota. So even after undergoing the tests you still won’t know what you wanted to find out. And why would you wish to find out? Will it make a huge difference to your life to know that you have a short or long time left to you? I would far prefer to be surprised when the grim reaper shows up.
In any case, there’s a much cheaper way of figuring out how long you have left. You have inherited your parents’ genes including telomeres, so the age at which they pop their clogs will give you a good indication of when you might expect to see the flashing celestial ‘game over’ sign.
This isn’t a scam of the same order as, say, the power balance bracelet con because there is some scientific basis for it, but it is a scam in the sense that it offers a service of dubious value for quite a high price. It’s an indication of my low opinion of my fellow human beings that I’m sure the test will sell like ice creams on a hot summer’s day.
Grumpy Old Man by Mark Widdicombe is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 2.5 License
Grumpy Old Man 
Wasn’t it curiosity that killed the cat? Not knowing when the gate to the one way path opens for one’s last journey is far more exciting than knowing when it does.
Even if it could be guaranteed that cell senescence is what’s eventually going to do you in, the error bars on this test will be wide. As you say, your parents’ longevity (or not) is just as good an indicator of your life expectancy.