Thanks for your comment about Renovations 3D. Phil Jordan has done a very good job by porting Java 3D and adapting Sweet Home 3D code to Android. I was pleased also to discover that drawing with the finger and modifying plan is usable on a tablet and even on a smartphone, with small changes to the computer behavior of Sweet Home 3D.
Nevertheless, a tablet or a smartphone + your finger will hardly replace the wider screen of a computer + a mouse, as soon as you want to be productive. But there are surely plenty of situations where this kind of portable device can be useful.