Farming, unfortunately, is a pretty locked-down market I've found. A couple of areas that you might look into though:
1. Long-range Wireless: This one can be a pretty solid money-maker. A lot of dryers and even storage bins now are using computers to monitor the contents of said dryers/bins. The ability for a guy to monitor his grain temps, make adjustments, or even shut down the system from his phone is a big draw for a lot of guys. Most dryer companies sell the dryer/computer/software as a package but the one thing they usually lack is a way to get internet connectivity to the location. That's usually considered the customer's responsibility and is where you come in. A lot of times it's not a huge distance to go from a source of internet like their house or shop to the bins but it's long enough (or through bad enough terrain) to make running a physical wire very expensive if not downright impossible. As a result, long range outdoor wireless networking antennas (like what ubiquiti or engenius have) can fill that gap and put a pretty penny in your pocket. They're simple to do (hardly any major interference in the sticks besides hills/trees) and usually pay pretty well.
2. Equipment Monitoring Camera Systems: This applies mainly to older equipment as newer stuff usually has this built in already. If you're not afraid to 'get dirty' and work on some farm equipment, farmer's will pay good money to add camera systems to their equipment. Things reverse cameras on grain cars to help them know what's behind them are in pretty good demand but the big one is boom cams. Boom cams are cameras that sit on the very end of the grain booms that point down and allow the equipment operator to know exactly where he's putting grain (in the event of a combine they can see where it's going in the cart, and in carts they can see where it's going in the truck) which prevents waste and ensures that one part of the cart/trailer isn't getting overloaded. Afaik there aren't any ready-made kits to buy/resell so you'd have to source parts and make your own solution but it's not terribly hard to source some heavy duty backup cameras from a car audio/entertainment distributor along with a couple of multi-source monitors. If you want to get really fancy and you know a little about electronics you can throw some relays together along with a couple sensors and get the video to auto-switch.
3. Security Camera Systems: Not strictly computer tech but security camera and dvr/nvr systems are popular among farmers who want to keep an eye on the place. You'd be surprised what people steal from farm places. Things like fuel from the fuel drums, fertilizer, even seed if it's left exposed. Can also be used to monitor livestock in the barns (especially useful during calving season) which is convenient.
As far as software and stuff goes though, most of that is already done by big corps who don't do reseller programs (unless you're an equipment dealer) so you probably won't make much inroads there. Otherwise, talk to some farmers and see what you might be able to offer them. If you can afford it and nobody in your area is doing it already, get a drone and do photogrammetry maps of their fields using those special IR cameras (I think they're IR). Farmers love data and usually won't bat an eye at spending a couple hundred dollars on a flyover if it means they can potentially add a few extra bushels an acre to their harvest.
