If you don't like paying attention to your DS, as I read in a guide, a good place for autorunning is in the Fuego Ironworks.

Over on the right there's a tile that shoots you up 13 spaces.

If you put something on the down arrow of your D-pad (I used the corner of a heavy book), and something on B (so you run), your character will continuously jog downwards and get shot back up.

The two main downsides to this are that the spaces you get shot don't count towards your step total, just the ones you run.

The other is that when your DS says "Oh!" you need to press B to start the hatching animation, and B again to refuse nicknaming the Pokemon. Otherwise it will just stall at that point until you notice.

I used this method to hatch a bunch of Ralts eggs and get a Buneary with a Sooth bell to max happiness at the level I caught it.

Marvelously automatic.