Mighty Mule FM200 Gate Opener $219 The Might Mule FM200 is one of the cheapest of the bunch at just over $200 and works for gates up to 12 feet long. Double the price and you can upgrade to the FM352 for dual gates up to 16 feet long.
Aleko TM AC1400 Sliding Gate Opener $218 The Aleko TM specs show it can open gates up to a whopping 50 feet long and 1,400 pounds, much higher than anything else in its price range thanks to its chain drive design. It's odd that it only comes with a 20 foot chain. When you've got a long distance to cover, this method is probably your only/best bet.
LockMaster LM901 Solar Powered Gate Opener $415 Don't worry about trying to figure out how to run power to your gate with this solar powered unit from LockMaster. Featuring a soft start and stop, this unit works with both a battery and the included solar panel. Upgrade to the LM902 for dual swing gate action.
USAutomatic Sentry 300 S $795.66 The USAutomatic model is listed as "commercial" grade and from the look of the reviews on Amazon it's fared quite a bit better than the LockMaster. It's also a lot more expensive, over double when you purchase the optional solar panel kit.
Most models come with remote controls and are operated by DC or AC power with a transformer. Safety stops when there's resistance is generally par for the course. Fences sold separately of course. Many of these manufacturers sell much more expensive models that are likely much more reliable (if anything can be taken from their product reviews on Amazon), so it might be a case of "you get what you paid for" but at these prices, it might be worth a shot. (Images: Amazon, Mighty Mule)