Drones have been used in the past to bring sensors to hazardous and hard to reach environments. This video from Aerial Robotics Lab @ Imperial College London shows an aerial sensor placement method that involves installing sensors like darts. As the researchers explain:
The proposed method is based on mechanical energy storage and an ultralight shape memory alloy trigger. The developed aerial system weighs a total of 650 grams and can execute up to 17 deployments on a single battery change. The system deploys sensors of 30 grams up to 4 meters from a target with an accuracy of ~10 cm.