I already mentioned earlier one free Swatch beats/Internet Time app for iPhone/iPod Touch, Internet Beat by Thomas Cherry. Dennis pointed out in his comment that this app has a bug, because it updates once per second, and a centibeat is less than one second, so it sometimes skips a centibeat. This is a pretty minor bug. However, I have noticed a bigger one. Half the time, when you turn the phone from portrait to landscape, the number of .beats changes. This is because when the centibeats are displayed in landscape mode you are seeing the exact number of .beats, but when in portrait mode it is rounded to the nearest .beat, instead of simply truncating. For example, @199.50 becomes @200. This is like saying that 1:59:30 is 2:00. A clock should not do that. If you go to the official Swatch website you will see that the app is half a .beat fast when in portrait mode, or 43 seconds.
I also found another app, InternetTime by Jaewon Choi for $0.99. I have not tried it, but I can see from the picture that it displays a map of the earth in the background, with approximate areas of day and night. It also shows the current date, and unlike the other app displays leading zeros, such as @090 instead of @90.