windows would be the best target probably, and hooks might not be the best idea, but you can capture all kinds of input with the apis documented on msdn.
for example. although i'm not sure how good they are these days... i honestly can't remember exactly which technique i used but i managed to make a keylogger with excel/vba once with apis i randomly looked up on msdn - it was just to prove a point though, i haven't really done anything more elaborate than that.
the difficult bit is really getting code to run. that i have no idea about, but i've heard about exploits from time to time, usually when they are fixed :)
http://msdn.microsoft.com/en-us/library/ms997537.aspx http://msdn.microsoft.com/en-us/library/ms646293%28VS.85%29....
for example. although i'm not sure how good they are these days... i honestly can't remember exactly which technique i used but i managed to make a keylogger with excel/vba once with apis i randomly looked up on msdn - it was just to prove a point though, i haven't really done anything more elaborate than that.
the difficult bit is really getting code to run. that i have no idea about, but i've heard about exploits from time to time, usually when they are fixed :)