A mailbox LED light that lights up only when it is dark (light sensor variable resistor) AND when the door is open (door sensor). It needs to run on batteries (at least 3 AA, possibly a 3 V coin cell, or 3 AAA batteries) and some way to transmit a small signal wirelessly from the mailbox to the house (you may use 2 Arduinos with XBee wireless shields or something else). The indicators will be: green to indicate mail in the mailbox, yellow for outgoing mail, and red for no mail. Hope this helps. Thanks.