Secure keyboard entry with JavaScript or Flash?

Is it possible to perform secure keyboard entry (similar to what is offered in the OS X Terminal app) using only web technologies and/or Flash?

If not, is there any way to more broadly guarantee exclusive/isolated access to input devices, or to check whether or not a device has been read or manipulated by external processes since start of observation?

I assume this is impossible with JavaScript alone, however I am not familiar with Flash and have heard of more extensive capabilities being offered (usually hear about them being abused) than JS would permit.