Swiss researchers say they\'re developing a system that will let sheep alert their shepherds if they\'re attacked by wolves -- by sending a text message. The system is centered on the use of a collar that contains a heart monitor that registers when the sheep become frightened and a text message, or SMS, transmitter, researcher Jean-Marc Landry said. The system has reportedly been tested on a small group of sheep that were placed in an enclosure with two wolf/dog hybrids -- which were muzzled. The change in the sheep\'s heart rate was enough to distinguish when the animals felt under threat, rising from 60-80 beats per minute up to 225 when the wolf/dogs were allowed to approach, researchers said. \"This is the first time such a device has been tested in the field,\" Landry said. The researchers said they hope to release a prototype later this year and test it more thoroughly in France, Switzerland and Norway, TG Daily reported.