Of course, such convenience doesn’t come cheaply. The MicroTAC Lite, which will be available from Motorola and from cellular carriers by the end of the month, will sell for slightly more than $1,000. Japanese manufacturers Mitsubishi and Fujitsu are said to be at work on still-smaller models. But at some point the competition has to stop. If the phones get much tinier, it will be too hard to punch the buttons.