IBM will be showing the latest version of its prototype Linux watch at CeBIT this month. The WatchPad, is the result of IBM's collaboration with watch maker Citizen, and was first unveiled last October, but this will be its first big public outing. IBM had previously demonstrated Linux-based watches developed independently of Citizen, but the WatchPad is the first such device that do much besides just tell the time. Visitors to CeBIT will be able to see the closest yet to a shipping model. WatchPad 1.5 features a pager-like application for sending and receiving short messages. It also has Bluetooth and infrared connectivity for connection to a notebook PC, and a fingerprint sensor for user -- or wearer -- authentication. Linux 2.4 runs on a 32-bit RISC processor, the frequency of which varies from 74MHz to 18MHz to help save power. By tinkering with Linux, IBM has reduced the amount of memory required to run the OS. In turn, this has helped increase the battery life to six hours. IBM has predicted all-day battery life will appear in a year or so. The operating system resides in 16MB of Flash RAM, and the Microwindows user interface is displayed in its tiny 320x240 pixel LCD screen -- this resolution is comparable to that used in the displays of handheld PDAs. Earlier versions of the WatchPad had an even higher resolution, with 640x480 pixels crammed into a screen 22mm by 16.45mm. This display had a 27.4mm diagonal -- that is just 1.08in. Such high resolutions are attained by using Organic Light Emitting Diodes, which are capable of achieving densities of 740 pixels per inch. There is still no indication of when the WatchPad will ship, but IBM is understood to be working with Citizen in an effort to bring the device, or something very similar, to market. Hewlett-Packard is working on a similar effort with Swatch. In trials in Switzerland, wearers can pass through a train station turnstile while the watch charges their bank accounts for the cost of the ticket.