If you are using Android 4.2, then you definitely have to check out DashClock Widget.
DashClock is a replacement lock screen clock widget for Android 4.2+. It also exposes additional status items called extensions. The widget comes bundled with extensions that give you instant access to:
• Your current local weather
• Missed calls and unread text messages
• Your next calendar appointment
• Unread Gmail inbox or priority inbox conversations
• Your next scheduled alarm