I once wrote a top-like tool in Oracle's sqlplus client, that is
not designed for building self-refreshing terminal UI display apps. Just to see if I could do it, had to get creative too. Used pipelined PL/SQL functions with never-ending output stream and a sleep function within it and had to carefully match the sqlplus "fetch array size" with number of rows returned in a batch from the pipelined function. Called it MOATS - the Mother of All Tuning Scripts - and then someone took the idea further and built v2.0 with added colors and charts, etc:
The v2.0 UI GIF is here: https://github.com/dbsid/moats_rac