You may want to look into the following possibilities for your intended project. I personally think your project holds promise especially for the elderly and disabled person.
OpenCV is not compatible with VB.net however EMGU is a wrapper that allows you to use OpenCV through VB.Net.
And finally a Code Project post (C# unfortunately but you can convert the code to VB) to get you going with EMGU:
Creating Your First EMGU Image Processing Project
Good luck, it sounds like a very interesting project indeed.