From the March 2009 issue of Entrepreneur

If you're thinking about creating a web app--whether as a business or to use in your existing business--its construction costs and time can run the gamut. It depends on many factors: how complicated the technology is, what tools you use to build it and so on. But details aside, here are a few web app entrepreneurs who show us it can be done.

Iotum Calliflower
Founders/ages: Alec Saunders, 45; Howard Thaw, 52
Launched: June 2008
App: A meeting tool that bridges businesses and social networks to allow the planning of and participation in interactive conference calls
Why it works: The solution is all-encompassing: It combines high-quality audio conferencing, scheduling, file sharing and collaboration in an easy-to-use interface.

MedApps
Founder/age: Kent E. Dicks, 48
Launched: 2005
App: A two-part application that provides a remote health-monitoring solution; the mobile app collects patient data and readings that a health-care professional monitors via the web app
Why it works: MedApps makes remote health monitoring accessible and inexpensive to the more than 133 million people in the U.S. with at least one chronic condition.

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Inspired to build your own web app? These sites can help you take that first step.

Ustream.TV
Founders/ages: Gyula Feher, 30; John Ham, 30; Brad Hunstable, 30
Launched: 2007
App: A destination platform for streaming live video over the internet; includes co-hosting, chat and hyperlink overlay functions
Why it works: While YouTube hosts previously recorded videos, Ustream hosts live content, allowing real-time viewing and interaction.

Just Uptime
Founder/age: Chris Phillips, 25
Launched: June 2008
App: A website- and server-monitoring application that provides instant e-mail notifications, SMS text alerts and detailed reporting when your website or server is down
Why it works: Sure, a few people out there spend every waking moment online. But for those who don't, this intuitive app gives them a heads up when issues arise.

OoVoo
CEO/age: Philippe Schwartz, 44
Launched: 2007
App: An innovative video service for creating video messages, real-time video chats for up to six people and live video calls
Why it works: Communication, whether between friends and family or employees and business partners, has moved online. OoVoo allows face-to-face conversations when being in the same room isn't possible.