You didn’t bother to mention an O/S.
Ubuntu Linux 11.10 (and probably most up-to-date flavors of Linux) have the mountpoint command.
Here’s an example on one of my servers:
$ mountpoint /oracle
/oracle is a mountpoint
$ mountpoint /bin
/bin is not a mountpoint
Actually, in your case, you should be able to use the -q option, like this:
mountpoint -q /foo/bar || mount -o bind /some/directory/here /foo/bar