PlantLink Wireless Plant Sensor Indoors Outdoors. Monitors Soil Humidity and Sends Alerts When Plants Need Water PLANT-SPECIFIC ALGORITHMS REMOTE MONITORING FROM ANYWHERE WITH FREE iOS APP INDOORS/OUTDOORS LONG BATTERY LIFE MONITOR UP TO 64 PLANTS WITH A SINGLE BASE STATION-UP TO 100yrd RANGE. Use this ASN B00U1QX19U, to order more sensors.