Water isn't good for gadgets, although not for the reason you probably think.
It's not the risk of shorting something out when you first get it wet. In fact, most phones, MP3 players and the like will carry on working after a brief dunking — at least for a while. Even if they're not waterproof, they're sealed enough that you have time to turn them off before the water seeps into anywhere it shouldn't.
The problem isn't the water as such. It's what's in the water — enough minerals and impurities to act as a conductor, making a connection between two components that aren't supposed to connect. And that can happen even after you've left your phone to dry out, if the minerals get deposited in the wrong place.
The usual advice to dry out a phone is to leave it in a bag of rice for a couple of days. Like the little packets of crystals you find in packaging, the rice absorbs the water and makes sure all the nooks and crannies inside the phone are dry. But that won't clean out any dirt that's got inside your phone and it won't get rid of any conducting deposits.
Reviveaphone takes a very different approach; for a start, it involves getting your phone even wetter. It's a strong-smelling liquid that you soak your phone in, which seems odd when you want to dry it out. But it's isopropanol, which you might know as circuit cleaner if you've done much soldering. It smells like strong nail varnish remover or dry cleaning fluid; it evaporates quickly, and it should take mineral deposits with it, leaving a functioning phone.
I tested it by simulating the most common way phones get wet (dropping out of a pocket into a puddle or toilet); I dropped a working, running HTC Desire into a sink of water. I left it there long enough to exclaim "oh no, oops, oh dear" a couple of times and fished it out. (Reviveaphone's PR sent us a Nokia 100 to test the product with, but given how robust Nokia phones are it didn't seem a hard enough test — Nokia phones have worked after being retrieved from a couple of weeks sitting in storm drains and my Lumia 1020 has just wiped dry after I've used it to take photos in the rain.)
Following the instructions, I turned off the phone, took out the battery, SIM card and micro SD and put the phone and battery into the pouch. It took a few attempts to open the child-proof cap on the Revivaphone liquid (in reality, you would have to buy or at least find the box, so this time shouldn't be critical) and the warnings on the back about not spilling or inhaling it are disturbing. I poured the liquid into the pouch over the phone and battery; there is actually too much to fit with the phone and battery in so when I pressed the seal at the top together some isopropanol spilled out; it didn't burn or irritate my hands though.
With the pouch finally sealed (and my hands thoroughly washed) I waited the seven minutes and opened the pouch. That was also unexpectedly fiddly as the top of the pouch tore as I opened it. I took out the phone, put it in the supplied plastic tray to dry, poured out enough of the liquid that I could retrieve the battery and left that to dry, then turned on the cold tap and tipped the rest of the liquid down the sink. Don't be tempted to put your phone in the airing cupboard to dry out at this point; the packaging notes that the fumes could be flammable.
Twenty four hours later, I was ready to put the battery back in and try turning the phone on. Well, that was the plan, but the amount of liquid sloshing around inside the screen deterred me, so I balanced the phone at an angle in the tray to try and drain it and left it for another day. At this point the pattern of the tray was clearly visible on the base of the phone and it still had liquid on.
After another 24 hours, the result was much the same; the back of the phone was dry but it still showed the waffle pattern of the plastic tray and the fluid inside the screen was still visible. I waited another day but the liquid was still trapped in the screen and when I tried the battery in it, the phone didn't switch back on.
Still, in theory, until more phones come pre-coated with waterproof nanocoatings, a kit like this is a good idea: the company says it has a 90 percent success rate. In practice, you'll want to save it for a phone that you've got too wet to try the rice trick on because it's not guaranteed to rescue your phone (and the money-back guarantee covers the £14.99 price of the kit rather than your phone).
Every dunking is different, as is every handset model, so Reviveaphone might keep your phone working — or it might not.
If you plan to take your phone somewhere damp (like the swimming pool or the edge of the bath so you can play music while you soak), pop it in a waterproof bag like a LokSak. Otherwise, it's safer not to keep your phone in a pocket that's likely to spill it down the loo or into a puddle.