First of all, Android mobile devices are not synonymous to a PC with a conventional HD. What you can do, assuming you haven't done so already, is to encrypt your Android tablet under Settings>Security. Once done, just do a factory reset. You should be done.
Apple mobile devices do this automatically. They encrypt personal data by default. When you do a reset, it just securely erases the device encryption key. It doesn't need to secure erase the data as its unintelligible anyway. In fact, I liked this idea so much that I've setup a similar environment with all my desktop and notebooks.