You need 3rd party software. It works with some cameras but not others. As far as I know it only works with cameras that have digic III/IV processors, but I don't know if it works with ALL cameras with digic III/IV processors. It seems to work with most of them though.
See this reference -
http://astrojargon.net/EOSInfo.aspxIt should work for the XSi (450D) but may not work for the T1i (500D).
To the best of my knowledge (and despite some other internet postings), there is no way a user can get a meaningful shutter count from early DSLR cameras up to the EOS 30D.
1D(s) series cameras are different and you can get a shutter readout on them.