I already wrote rtd client
'RTDman' last year in c++ for same reasons. Its GPL so you can look at source code. Its console application. Only works with NOW/NEST
Josh/Shankar have backfill tool that is now also a GUI for RTDman. GUI is in active development now so may have some bugs.
EOD - i dont need it, there are some open source tools ( hajika / NSE EOD Data Downloader v3.0 / ABCD ) that you can look into.