I do what you're asking with Garmin. I have a 130+ unit on the handlebars, recording GPS data and pedal power-meter data. I create segments on the webportal for Garmin Connect. These segments can be loaded, selectively, to the 130+ headunit. While riding, the unit advises me that I am approaching a segment, and, when I'm "on segment," it tells me whether I'm ahead or behind my best recorded pace by X number of seconds.