Yahoo has an article about a GM flower that turns red when in the presence of nitrogen-dioxide — material that evaporates from land mines. This sterile plant can be sown over a suspected landmine field and the resulting red plants act as a marker for areas that need examination.
See Yahoo! News – Flower-Power Could Help Clear Land mines for the full story.
I wonder how long it takes before a landmine starts throwing off NO2? If too long or if the mine is too deep, this many have limited potential, but it sure looks pretty cool to me.
They also appear to have a GMO to detect heavy metals in soil.