BLE + Sensors + Battery in a plastic. We already done 85% of your product.
SensiTHING Environmental Monitoring Module with Wireless Charging Capability
Application note: How to add AA battery To SensiBLE 1.0 or SensiSUB 1.0
This IoT Starter Platform Also Helps with What Comes Next
From Bluetooth Low Energy to Cloud : SensiBLE IoT node use case