I need to trigger an electric imp to wake from deep sleep on the event that a liquid level sensor is exposed to water and send an alert to a user. This device periodically wakes up out of a deep sleep state and connects to a server to log sensor data (temp, humidity, light, water level in the tank) via wifi. I then would like the device to go back to deep sleep even though the water will still be present. This behavior will have to repeat every time the water level sensor goes from low to high (every time the user fills the tank). I am aware that the interrupt can only be triggered when the interrupt pin state transitions from low to high, and that the device can only go to sleep when the pin goes low again, hence the challenge. This is a battery powered application so power consumption is at a premium. Can anyone suggest a solution?