In this segment from Tuesday's Investor Beat, Motley Fool analysts Mike Olsen and Brendan Mathews each pick one stock they've got a close eye on today. Mike looks at Zimmer Holdings (NYSE: ZMH), and why he loves the market share and barriers to entry for competitors to this knee and hip replacement company. Meanwhile, Brendan looks into Western Union (WU -0.31%) and says he'll be looking very carefully at consumer-to-consumer transaction volume when the company reports earnings Thursday. If people are continuing to use the service, he could see the stock as very cheap today.