Please note: This addon will cease to work in 7.1 inside instances. Blizzard is removing the ability for addons to know where groupmates are in any kind of instance PvE or PvP. This is not something I can fix or work around. As of 7.1 this addon will no longer be supported.

When your grouped mouseover unit is out of range of spells, this addon displays an arrow beside your cursor pointing in their direction.

There's an option in the Interface Options Panel to also show the arrow for units within the range of spells.

The arrows are color coded:
Green: in range (less than 40 yards, if enabled in options)
Yellow: out of range but nearby (40 to 150 yards)
Red: out of range and far (150 to 500 yards)
Brown: probably in another zone (500 yards or greater)

This will work with any raid frames, including the default raid frames.

Special thanks to Javonthalas-Hyjal for help making this!