Sailing suppliers have something called a "Night Watchmen", a 12 volt photo electric switch. Google says these cost $35 and up, depending on where you buy it from.
For your EL wire inverter, I think it is important that you get the on/off "Night Watchmen" style rather than the electric dimmer style that gradually turns on at night by varying the voltage. Some EL wire inverters might hate being fed a low voltage during sunrise and sunset. Mine, at least, will start to flicker and seem to get much hotter than normal at very low voltages.
Some solar charge controllers have an output to turn on lights at night. They don't have an electric eye, they detect night through the solar panels. These can be nice because they have a low voltage disconnect, so that they won't let the lights completely drain the battery and damage it. Check out this one, $38, can handle 15 amps of solar panels, and has "16 programmable timers for lights and etc." Their in-stock/out-of-stock status changes quite a bit, so if you have smaller solar panels you could wait until the less expensive lower capacity one is back in stock:
http://www.virtualvillage.com/15a-12v-p ... 8-060.html
Though their website sucks, I have ordered a lot of stuff from Virtual Village for my mutant vehicle and have been very happy with how fast stuff arrives in the mail from Hong Kong (generally a week).
The solar suppliers have DC timers that are just like the AC timers, but more expensive-- $50-75, depending on if it is the LCD kind or the kind with the spinning disc:
(for the LCD kind)
For your swamp cooler, I think the ultimate is some kind of industrial Omron style cycle timer. I use one on my CNC mill to control a solenoid that blows chips away and am so happy with it. With one of these on your swamp cooler you could set it to 3 minutes on/5 minutes off, and easily adjust that with a twist of the knobs. That would save a whole heap of electricity and water. You can't really do that with a 24 hour timer. With two you could even have one on the water pump, since to wet the pads you may only need to run the little impeller pump for 5 seconds every 30 seconds, or something like that. McMaster and etc want to sell the expensive super-variable ones (from 0.01s to 300 hours), but there are cheaper models that have less of a wide time range (1-90 seconds or whatever).