These are the excepted leaders in the wireless game.  Nobody can tell you better about pocket wizards than Pocket Wizards so here is some stuff from their website. I agree with a large percentage of what they have to say. The Pocket Wizard Plus II transceiver is easy and simple. Four channels. It automatically knows when to be a transmitter or a receiver. And an auto-sensing hot shoe knows when you want it to relay the signal from your camera to the flash for remote camera work. It's just like breathing. It's so easy.  There is a reason until recently they held the market. No real competition. Because their real competition was Quantum. Their product now called Free Wire or something like that had a few glitches and some folks just had enough of the brand.  I own pocket wizards though I have Nikon Flashes with internal wireless.  I use them on my Vivitar's, Photogenic and Black Lines.

Their mantra is as follows:

• Eliminate unreliable Synch cords that get in the way of your creativity
• Allow you to position lighting where you want it, not where the Synch cord reaches
• Permit you to interact with your subject without the limitations of shutter release cables
• Trigger your flash and camera simultaneously to capture split second action at every angle
• Protects your camera (digital or film) from damaging high-Synch voltage

n addition all Pocket Wizard Radios are range-tested at distances substantially greater than their advertised ratings; only units that trigger 100% of the time are released for sale, their benefits are 6 to 24 bit Digital Coding, Long Range Triggering, Unsurpassed Reliability, Innovative Features and Universal "fit" on almost anything photographic.

The Pocket Wizard Plus II transceiver system does more than cut the cord. The Pocket Wizard Plus II can wirelessly trigger lights and/or cameras within a range of 1600 feet of the transceiver. Utilizing advanced wireless technologies, four 16-bit, digitally-coded channels are available for selective firing of lights, or when working in ‘crowded’ environments. If speed is a concern, images can be captured at a rate of up to 12 frames-per-second, which outpaces most currently-available cameras, pro or otherwise. Ultra-fast microprocessors allow for top sync speeds of 1/250th-second for focal-plane shutters and 1/500th for leaf shutters.

The Pocket Wizard Plus II is compact, with a short, unobtrusive, rubberized antenna. The total height of the transceiver and antenna is less than 6.5”, and it weighs in at 6oz including the batteries. To ensure a secure fit to your camera or bracket, the Plus II features sturdy locking rings for hot shoes. Power is supplied by 2 AA batteries, which are good for about 60 hours of playtime. An optional AC adapter allows for continuous, unlimited shoot time.

Fast ‘plug-and-play’ set-up times. Simply power up, choose a channel, connect your flash cable and you're good to go.
Auto-Sensing Transceiver Technology enables the Plus II to switch back and forth between transmitter and receiver modes as needed for greater flexibility on the job. All Pocket Wizard transceivers default to receiver mode. When a hot-shoe or other trigger is detected, it automatically switches to transmitter mode.

If your cameras and lights will be positioned apart from one another, the Pocket Wizard’s Auto-Relay Mode wirelessly triggers remotely located cameras and flashes within a 1600’ range of one another. A choice of four 16-bit, digitally coded channels enable you to simultaneously trigger all of you lights at once, or isolate one group of lights from another for more complex lighting arrangements. Multi-channel switching is also useful to isolate your lights from nearby lighting systems when shooting in close proximity to other radio transmitting devices.

Sports and action shooters can confidently shoot flat-out regardless of which camera you use, thanks to the Plus II’s ability to trigger your camera at a sustained rate of up to 12 frames-per-second. Ultra-fast microprocessors enable trigger-response times as short as 1/2000th of a second allowing for reliable sync speeds of 1/250th for focal plane shutters and 1/500th for leaf shutters.

Mini-phone connector cables are available for all major brands of lighting equipment in a variety of lengths of up to 16’. A variety of dedicated camera triggering cables are also available for most popular camera systems. Thoroughly compatible with earlier-version Pocket Wizard transmitters and receivers. Equally important is the fact the Pocket Wizard Plus II communicates fluently with all Pocket Wizard-enabled photo gear for maximum flexibility on the job.

QUANTUM 

Medium Priced - ELINCHROM SKYPORT
(General Bugs and Fixes Recommended by the Great minds at Strobist.Com)
There is an excellent article on the STROBIST about a conflict involving these two components. Elinchrom's Skyport and the VIVITAR 285HV.  Here is the workaround they  came up with for the 580EXII which also applies to the Vivitar if it shows the same bug.  Simply put the receiver does not trigger the flash. It's about "bandwidth or pulse signal". A small capacitor in line (22nf capacitor) increases the pulse length and it works flawlessly.  You do this at your own risk but this is a fairly safe fix and not that complicated. Later tests and the resultant conclusions indicate this is the problem and the fix. Towards the end of the thread, he explains that he measured the duration of the pulse emitted by the Skyport receiver when triggered, that he estimated that it was too short for the Canon, and that he lengthened the duration by adding a capacitor on the sync cable.    To recap: solder a 22 nF capacitor somewhere in parallel on the sync cable and you are done.

Low Cost -  eBay Specials 
R616 and 604 UNITS
These units work and have a few quirks but overall the bang for the buck is a substantial savings over the cost of Pocket Wizards and other highline transmitters if you are on a budget. BUT like anything else that comes from the land of fish heads and dog meat be aware their failure rate is sometimes higher than acceptable to some and the resultant losses in both patience and possible shots may get you mad.  With that said they are a good mix with the Vivitar's if you change the feet on the Vivitar to a simple metal foot with PC and ignore the weird pin the Vivitar normally uses.

Cactus V1-V2