We have attempted to fill the gap in Android where it has otherwise been left out.
http://www.talon-designs.net/andcad.htm
There is a demo (as well as a full version) available on the Android market, which will give you an idea of wether or not the feature set is ideal (or close to ideal) for your needs. Just search for "AndCAD" and you will find it.
Currently it supports a proprietary format that we created, but does allow for DXF import and export. (DXF format is currently in beta, but is improving steadily).
It supports your basic drawing commands: lines, polygons, circles, polylines, etc. It also supports layers, snapping, ortho/iso drawing, minimal line types, image import, and a handful of other features. The next release will have support for direct input as well as dimensioning. Following that is support for block libraries, mirror, offset, etc etc.
Regarding DWG format. Since the DWG format is proprietary to Autodesk, we have been unable to implement the abilities. The cost of licensing the "Official" DWG format is way to high for us to be able to proceed, unless we can get support in that area. If I recall, its about 2500 to licence the libraries necessary to implement it, and a yearly 1500 maintenance fee to continue. Unfortunately, we cannot afford said costs as of yet. That being said - it doesnt mean that it is out of the question. Just not in the books currently.
Anyway - feel free to let me know if you have any questions.