There are 2 packages in  AUR:
-- 1 in community:
 cwiid: follows the cwiid official releases.
In order to install cwiid run as root simply:

pacman -Sy cwiid

-- 1 in unsupported:
 cwiid-svn: follows the svn revisions.
In order to install cwiid-svn follow the isntruction in the archlinux wiki:  How-to use AUR.

Please note that:
-- The 2 packages are mutually exclusive: you can't have both installed at the same time.
-- In the svn version you have to modify the pkgver (at the second line of  PKGBUILD) according to the revision number that you want to checkout and compile from subversion repository.

Please report any problems regarding archlinux packages in the AUR package's comment section.