Gear for incline - Internal Gear Hub?
By using a larger sprocket and/or smaller chainring, you can gear an internal hub to cope with just about any gradient. (There is an eventual limit where input torque can destroy the hub.)

(Edit: @Rider_X is right that the Shimano limit is more restrictive than I remembered. There are people using lower gearing and reporting no problems, but you might have to be careful. On the comparison chart below the Rohloff could be geared quite a bit lower (30:16 rather than 44:16, see Rohloff), but the Nexus is following Shimano recommendations according to this forum post))



A cheap hub will give you three gears with big gaps between them and a limited overall range, and although you can make the bottom gear low enough for a steep gradient you might find it too restrictive; a very expensive Rohloff hub will give you 14 gears with gaps and range comparable to a derailleur system (but without overlapping or duplicate gears - a 27-speed derailleur system doesn't have 27 usefully different gears).
In between those, there's a range of hubs available giving you more gears, more overall range, and smaller gaps, as you pay more. See, for example:


http://www.cyclinguk.org/cyclists-library/components/transmission-gears/internal-gear/internal-gear-ratios
https://hubstripping.wordpress.com/internal-gear-hub-review/