The dungeon editor runs in a browser without any plugins. I do not have an iPad, but I'm developing on a MacBook with safari (without flash) and this performs quit good. A friend of mine tried it with a iPad on the table for the players and he used a Windows PC for his dungeon master view and he didn't ran into any problems.

And I think for a similar tool for maps (and maybe even city maps) I can use the same technic. Of cause this doesn't have to be grid based, and coasts and rivers seems to be the biggest challenges to me right now.