We use these in X-Wing a ton, but I don't seem them discussed as much here. Since not everyone here plays X-Wing they may not know about these so I thought I'd post something.
http://usshop.thearmypainter.com/products.php?ProductGroupId=5
It's a small laser pointer, but emits a line rather than a dot. That makes it very quick and easy to check arcs without trying to fit a ruler between a bunch of ships, or in Armada's case that furball of fighters.
The one I got from my LGS is great, nice and bright, and the line can reach a couple feet if I hold it up high enough. So more than enough for Armada.
Shipping is kinda spendy there, for me in the US it was $8 for a $9 item, but if you can get one at your LGS I highly recommend it.
