I talk to them.
Technology cannot solve social problems. You have short morning standups. What did you do yesterday? What will you do today? Any impediments?
If something sounds fishy (or I'm curious), I stop and ask questions: "You were working on XYZ yesterday, how'd that turn out?". This forces people to pay attention, and to actually know what's going on. It also keeps you the team lead in the loop (and paying attention, and knowing actually what's going on). This needs to be on time, and short (10 minutes max). Anything else and people won't "shelve" work. They'll stop and wait for the standup and then take time to get started again. Some will do that anyways, but it's largely unavoidable.
Then I stop by everyone's desk in the afternoon. Not every afternoon (though it might be more than every afternoon for new people), not at the same time, but around the same time (so it's both informal, and regular). "Any problems? Any impediments?"
You'll be surprised how often you'll encounter problems when people are one on one.
If people have no problems, great; get back to work. If they don't have problems all week? Problem. You're not challenging them enough, or they're not opening up. Ask how XYZ (that they mentioned in standup) is going. Make them explain things.
This isn't micromanagement. You're not telling them how to do their jobs. You're not babysitting them. You're there to remove impediments from their day to day life. You need information to do that. As long as you keep your team out of meetings, and project managers out of their cubes, then one person stopping by to help once a day isn't going to cause them grief. But all these interactions need to come from the "I am here to help you" vein.
Another thing I will do is review changesets (by myself, informally). I can then see how frequently people check in, how large their changesets are, how that matches what they reported, how often they re-do things, how many bugfixes they have, and so on. A work item changing status to "done" is nearly meaningless. Look at the code. Does it seem done?
note: One extremely serious side point: how big is your team? Is it more than 7 people? Of course you won't be able to keep track of everything going on if your team is too big.