I've been testing a lot of different non-pyrotechnic signals for work lately.
A few observations:
Greatland LaserFlare: Awesome device, but very directional. The green version is best for both day and night signalling. Not cheap though at $250 retail. They have a smaller red version for under $100. It would be best to have a strobe or other more omni-directional light to use in conjunction. But when you see it, there is no mistaking it.
Surefire G2-LED Flashlight (or similar): A very visible light from over 20 mile distance. Momentary switch allows Morse signalling. The reflector is very important for maximum visibility. Has good visibility up to 35° from centerline (70° spread).
We found that many tactical strobes made poor rescue beacons. Strobes need some sort of reflector and/or diffuser to make a large illuminated spot. Some of the tactical strobes were very bright but made such small targets, they weren't as noticable as some weaker lights which produced a larger target.
Strobes: Most strobes max out at around 5 miles or so.
FirstLight Tomahawk LE (120 lumens) has an exceptional strobe beacon, but it's complicated and the switch has a small drain on the battery so you don't get the storage life of some beacons. We got about a 10 mile range from it. About a 75° to 80° beam spread.
PowerFlare strobe is not as powerful as some but it's very versatile with 9 strobe settings including a flashlight mode.
Adventure Light VIP-Survivor is a versatile light with steady-on, SOS, and steady flash mode. It's small, bright, with a 180° beam spread. Very visible and noticeable. The great part, 300 hours of strobe one CR123A lithium battery or 100 hours of steady light. can be easily clipped to your gear. About a 5-6 mile visibility. Weighs 4 oz.
Xenon Strobes in general: Most are very bright going out to 3-5 miles visibility. Not as durable as LED models, or efficient on battery use, but they are more common and often less expensive. Princeton Tec and TekLite make several versions of these as well as ACR.
I'm ordering an Energizer Hard Case Tactical 2AA LED flashlight next to check it out. It has some interesting features like both visible and IR strobes.
Prioritizing I would have:
1. Surefire G2 LED or equal, MSRP $65
2. Adventure light VIP Survivor, around $80
3. Greatland Green Laser Flare. MSRP $250
We observed the signals which were on a boat, from an aircraft at 3000 feet, and from another surface craft.
Surefire ought to made a optional strobe end cap they could sell for their flashlights. It would make a nice light even more versatile.
Cheers,
Tom