Here is a Bluetooth data logger with internal and external sensors to monitor shallow water and soil temperatures. The HOBO MX2205 TidbiT Data Logger is designed to withstand harsh environments. It has a response time of 20 seconds. Its temperature sensors have a range of -40 to 100C and -20 to 70C respectively (fresh water / air).
The internal sensor measures ambient temperature while the external sensor measures water or soil temperature. The companion app lets you check logger’s status, create audible alarms, and export data in CSV, TXT, and other formats. The logger has a rate of 1sec to 18 hours.[where to get it]