We have a segment timer that sat in a box for about 4 years before I got it out. Works really well for us. But, an option is to use a timer, like Seconds Pro, on an iPhone/iPad connected to a PA system ($150 at Costco). Can play music over the PA and the timer kicks in over the music when it's time to change. I've been using that in the weight room and I connect it to the stadium PS system when we practice on the game field. Lot cheaper than buying a segment timer. Only issue is there is no clock to see, you just have to go with the audio.