Nvidia's core business is graphics cards for PCs based on x86 CPUs. It's thus interesting that Nvidia is betting so much on mobile, even if the mobile market is exploding so quickly. The mention of ARM, however, is not so curious.
Nvidia sells the Tegra system-on-a-chip series for mobile devices such as smartphones, PDAs, and other mobile Internet devices. Each Tegra version integrates the ARM architecture processor CPU, GPU, northbridge, southbridge, and memory controller into a single package. Nvidia is trying to have the Tegra name emphasize low power consumption and high performance for playing video and audio, but so far the series hasn't been particularly successful (it has made an appearance in the Zune HD and the failed KIN). As the importance of powerful smartphones grows, we should see Tegra grow as well.