On October 17th, some Lebanese found an Israeli electronic sensor on their side of the border. The Israelis soon became aware of this, and destroyed the device from the air with a missile, or internal explosives. There are conflicting reports. But Hezbollah fighters showed up shortly thereafter, and searched the area. They found another such device, and blew it up. It's believed these devices were for tapping into telephone conversations. The Lebanese believes that some, or all, of these devices were equipped with explosives, to self-destruct (or be detonated remotely from Israel) if discovered or tampered with.
Since Lebanon arrested dozens of Israeli agents in the last year, apparently with the help of Iranian intelligence operatives, Israel has apparently increased their use of electronic sensors. These detect movement, sound or electronic transmissions. Many are buried, or otherwise disguised to make detection difficult. Hezbollah has become aware of these devices, and offers rewards for those who find them. Thus hunting for Israeli sensors has become a popular activity along the border.