I would recommend you do not implement this.
The information you are looking for is always available through pace inspection CTRL+ALT+F1
And if there are a couple of pages where you want it displayed in the page you can do that with a page extension.
Avoid making this a global thing because you will have to maintain it as pages are changed and added.
In my experience this is a typical request that comes from user that are not very familiar with the system and as they grown more experience in using the system they no longer see the need for it.
Using a fact box you would have to have one factbox for every table in you want to display the data for.
Using a codeunit you could do some fancy stuff with recordrefs - but you will still have to add an action to every page.
Page inspection is there always by default out of the box.
