As a badge count there is no standard way of doing this. However, one of the ways to do it in a simple way is by adding badge num on your application icon in launcher. It is handled by using a broadcast receiver. All the handset doesn't provide badge count, it fully depends on the manufacturer. Badges count function works really well with LG, Sony, Samsung, HTC.
For better understanding, let’s see an example, how badges are shown in Sony Ericsson and Samsung handsets: