Could someone explain to me how a skinlink for a comm works? (p. 318 SR4) The rules say that

The skinlink on your commlink would allow you to communicate with any other electronic device that has a skinlink and is touching skin (some GM's allow gloves/clothing in between the device and the skin, YMMV). Thus, a skinlinked commlink could talk to a skinlinked set of glasses (glasses touch skin at the nose and by the ears) to display AR but if your skinlinked commlink wanted to communicate with, say, you're teammate's commlink you'd need to rely on the normal wireless capabilities of your commlink and not the skinlink --- unless, of course, your buddy's commlink is skinlinked and he/she's touching you.

Such a link is almost completely protected in that the communicates could only be intercepted within your PAN if the hacker is touching you and also has a skinlink. However, remember that if the commlink itself is hacked, which it can be if it's wireless signal is active, then your devices are still vulnerable. However, skinlinks remove the possibility of intercepting the wireless device traffic and spoofing commands via Electronic Warefare. Also, don't forget the jamming part of the RAW quoted by the original-poster. If an area jammer is thrown into the middle of a gun battle, smartlink bonuses may just fizzle if the communication of your wireless smartlink is jammed. My PC's hated that one

Why would a character not want it? Because they're not tech-savy or short on cash. Or, if you're GM is a stickler for the rules and argues that wearing clothing breaks the skinlink then it might be better to use a non-skinlinked commlink and wireless communication and wear normal disguise pieces like gloves and masks.

Lastly, for combat scenarios I've run, the hackers have never been able to actually intercept the wireless traffic nor have they been able to hack commlinks before the rest of the team kills the person they're trying to hack. The only time someone did successfully hack another person's commlink in combat was only because she made the rest of the team promise not to kill the guy she was hacking until last so that she could hack him at all. Thus, skinlink is, primarily, a flavor-based paranoia thing and, in my games, has not been a useful addition to commlinks and devices.

As always, YMMV.

Dashifen's response was about as good as you can get. I second it across the board.

http://forums.dumpshock.com/index.php?showtopic=11802

One idea I had for hacking into someone's skinlink was to hack it and then start rapidly fluctuating the temperature that they felt making them go 75C to -20C in a flash. I'll admit that I haven't tried to hack a commlink yet... I'm a mage afterall and that is what chaotic world is for.

Unless they also have a touchlink, that isn't likely to work - skinlinks don't override perceptions of reality - they're merely replacements for cables.

Ok here's an odd question:

If a character with a skinlink is hit with a shock baton or shock hand, would that fry all of the skinlinked devices?

More fun:

If you have a skinlink and shock hands, would the shock hands have to be shielded to keep from frying your own skinlink?

You're confusing touchlink with skinlink.

Skinlink is simply a way of transmitting data across human skin. If you've ever had a physics class where you make a human chain with the person at one end holding the live wire on a power source and the person at the other end holding a flourescent tube, the human body is capable of harmlessly conducting a couple of watts of (specifically tuned) electricity. Skinlink uses that ability to transmit data to other devices in contact with the host's body.

Touchlink is the sim-sense tech that lets you get physical sensations from AR or BTL. Not a common bit of tech, really. How often do you need to feel the temperature of a volcano or the skin of a snake from an Indiana Jones vid?

Skinlink is using modulation of the EM field of the human body to transmit data.
The rules require touch range, not nececarily skin contact, too, so basically,gitting elektrocuted may cause 'noise', but usually won't kill the devices.

I find the Skinlink to be useful for my Technomancer. It allows silent and non-detectable communication through the Living Persona and gives a node to store data on, compile sprites, or whatever else. Otherwise a Technomancer has to transmit a wireless signal or use trodes, even to local devices, which sucks if you're sneaking in somewhere or anyone nearby is good at EW.
Which brings up my point again that Resonance shouldn't decrease with essence. Then a technomancer can just get a freakin' datajack like everyone else and doesn't have to deal with skinlinks.

Hrm, actually, Skinlink isn't that great for TMs - they only have a natural WiFi link...