Hi! I am making an arduino project where i am monitoring the temperature of my cabin, and obviously i would like that system to work during a power loss. I plan to use an GSM-shield with the arduino, that will send me a message if the temperature drops under 4 celsuis. So, i want to make som kind of UPS-system for my arduino, to make sure that it can stand a 1-2 day long power loss. I want it to be fairly cheap, (sub 50 usd), and i wonder if you have any ideas for easy circuits? It doesnt need to be perfect, so it doesnt matter if there is a small delay when it switches over to the battery. I have acssess to a 9/12v (1 amp) charger, and unlimited supply of resistors, leds and transistors. Do you have any good, easy ideas for me?