This life expectancy test will calculate a rough estimate of how long you will live based on your age and your answers to the several test questions.
This app has a widget that count down rest time of your life.

References:
http://www.ncbi.nlm.nih.gov/pubmed/24296637
http://www.annualreviews.org/doi/abs/10.1146/annurev.publhealth.031308.100310
http://www.annualreviews.org/doi/abs/10.1146/annurev.publhealth.21.1.543
http://www.annualreviews.org/doi/abs/10.1146/annurev.pu.05.050184.002245
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2812%2961690-0/abstract
http://jama.jamanetwork.com/article.aspx?articleID=1710486