I wrote before about the MBtiles format, a convenient format to store tiled maps in a single portable sqlite database. Probably the easiest way to create them is with Tilemill, as described here. The format is supported by amongst others QGIS, but it is especially suitable for use with map viewers on your mobile device.
The format is now supported by various mobile map viewers, including e.g., Geopaparazzi and OruxMaps. One I like for its rich set of features is Locus Map Pro. I normally only write about open source, but I think the developer of this app deserves some credit for being one of the first (as far as I am aware of) to support the MBtiles format. Up to very recently you could only view maps in MBtiles format (similar to the other viewers mentioned above), but with the latest update support for the UTFgrid feature has been added.This basically adds interactivity to your map.
What does this mean? Well, if you create map that included parametric data (check out TileMill how to do this), you can now open the map in Locus Map, click on any location and you will get a popup with the attribute data for that location. See the screenshots below.
This brings it close to a web-based map like this online map of the vegetation of Rwanda. Both the mobile map shown in the screenshot above (and which you can download from this site) and this online map are in MBtiles format, created in TileMill.