Is there any Firefox or Chrome add-on to highlight search terms (and jump to them ?)

I had this frustration too, and found that Googlebar Lite is a near-perfect replacement for the now-defunct Google toolbar. It allows most of the functionality of the original Google toolbar, but it still works with current versions of Firefox. The "marker" button for highlighting the search terms and the ability to click a search term in the bar to go right to it in the page both function perfectly in this add-on.

Google Quick Scroll for Chrome does what you want to some extent. It highlights the search term, and clicking on icon moves you to the search term

yes there is: SearchWP

"Jump-to-word buttons and highlighting for the search box content"

it converts the words you typed into the searchbar into highlighted 'buttons', click one and it jumps to the next occurrence of that word in the current page! It handles too many words to fit int he searchbar by putting a little menu at the side. It works beautifully.