teamviewer (just search teamviewer) have an app that will do that but it is limited to only certain tablets etc. I think you can use phone as controller - you can certainly use a PC.
This app afaik is the only one where you have complete control i.e. as if on tablet.
You have to be patient - there is a lag between pressing icon and it taking effect of a couple of seconds
There are a few e.g. airdroid where you have some control, but you can not see screen directly and you rely on end user sending "photo shots of screen to you" - very slow and cumbersome to be of great use (these type of apps would be better if end user did not usually have to hold two or three buttons to do a screen dump).