Responding to member smartphone usage, the $688 million Firstmark Credit Union in San Antonio, Texas, has added an Android app to the iPhone and Web-based mobile service it already had in its lineup.

“We have been closely watching the growth in Android device usage for some time. By December 2010, Firstmark Android users reached 30% of our mobile traffic, justifying the development of the app,” said Fred Hagerman, the 90,000-member credit union’s senior vice president and chief marketing officer.

The app was developed by a local software services company, Common Sense LLC, and offers balances, fund transfers, recent transactions and bill pay, Hagerman said.

Hagerman said 4,000 potential member-users were notified of the availability of the Android app.

“Given the potential impact on the call center for online banking registration, we’re spacing the notification campaign out over the next week,” he explained.

Hagerman said that so far this year, mobile views represent about 8.3% of Firstmark’s total Web page views. Of those, Apple’s iOS is getting 57% of those mobile views, Android is getting 39% of the mobile views and the rest is split pretty evenly between RIM (BlackBerry), Symbian (Nokia) and Windows mobile platforms, he said.