There are a few companies that offer development software for WAP applications. Some examples are Ericsson and Nokia.
The Ericsson Developers' Zone is a web site that offers developers access to various kinds of development aids and support for a number of different technologies and solutions, such as EPOC, WAP, Bluetooth, Mobile Positioning, GPRS, SMS and iPulse.
From this web site you can get various technologies to develop WAP applications. One example is WapIDE 3.0 a software development kit that enables you to test in your PC how your WAP application will behave on the Ericsson phones.
Also at Nokia you can get development software. For example there is the Nokia WAP Toolkit 2.1 that offers developers a PC environment for creating, testing and demonstrating WAP applications.