Transistor as switch with low leakage current
I don't really know much about transistors, alas, but I am looking to use a transistor as a switch in a device where it's important to me to that the batteries (3xAAA) last about a year. This means that I want to minimize leakage current. I would like to use about 20 mA at 2.7V to control 0.5-1 A at 3.3V (I have 4.5V at my disposal, so I can handle a 1.2V drop through the transistor). The device is a water leak alarm which I assume uses almost no current except when it's alarming.
Any suggestions on what to use?
A lot of people use TIP120s as switches, but I've also seen comments that indicate that they have an unpleasantly large leakage current. And I don't need the high voltage/current/amplification capabilities of the TIP120.
Or should I just use a solid state or electromechanical relay?