Latest Arduino project now includes a 4 line LCD display. DHT11 temperature / humidity module and a soil moisture sensor. The LCD displays the temperature in Celsius, humidity as a percentage and for the moment, the moisture level on a scale of 0 -> 1023. where 1023 is the reading you get in Air so is therefore very dry. Tested in a plant pot and there is a big drop on the readout picking up the fact there is moisture in the soil.
This sort of project is great for a greenhouse and could potentially be used as part of a automated plant watering system or just an overall monitoring system.