While the overall employment picture remains relatively bleak as the U.S. heads into the Labor Day weekend, two separate reports reveal significant growth in the online work marketplace. Specifically, demand for mobile developers has never been higher.

According to the August report from online employment platform oDesk, demand for mobile development skills is up 131 percent year over year, and employers spent $20 million hiring online during the month – an increase of 95 percent over the same period a year ago.

The hottest growth was reported in jobs posted for Android SDK, iPhone and Windows Mobile. Overall, a record 100,000-plus jobs were posted in the technology sector.

The growth in demand for mobile applications is thanks to the growing reliance on the smartphone for business and personal use, as well as the excitement around new product announcements – such as Apple’s anticipated iPhone 5 later this month – and cross-business deals like the Microsoft-Nokia partnership and the recent Google acquisition of Motorola. The oDesk Online Employment Report indicates that mobile application development was the eighth most requested category of work last month, with demand for Android SDK and Windows Mobile skills leading the category in new job growth.

“The continued innovation and development in mobile devices and systems has led to a surge in online employment opportunities for people with these skills,” says Gary Swart, oDesk CEO. “Businesses are going mobile, and talented developers from the on-demand online workforce are building the apps that will take them there.”

A different report from SimplyHired.com revealed that nationwide job openings increased for the second consecutive month, up 4.5 percent month-over-month and 16.5 percent year-over-year. Openings were previously up 6.5 percent month-over-month and 17 percent year-over-year.

“As expected, job openings continue to remain positive and stable this month due to the start of the fall season,” says Gautam Godhwani, CEO of SimplyHired.com. “We anticipate modest continued job growth through the end of the year from seasonal hiring.”