Looks to me like they're going to announce a new Android tablet. I hope it has even more streaming options to follow up to the Shield tablet. Maybe there's a possibility of increased Nvidia GRID integration?
Source: http://www.androidpolice.com/2015/02/10/nvidia-sends-press-invitations-to-march-3rd-event-teasing-a-gaming-product-5-years-in-the-making/
Source 2: http://www.nvidia.com/content/M2G/made-to-game.html
EDIT: Today's the day, folks! I will edit this original post once the event begins at 10 pm EST tonight.
EDIT 2: The NVIDIA SHIELD, an Android TV set-top box has been announced! Running the new Tegra X1 Mobile Superchip!
EDIT 3: Price set at $199, will come with Shield game controller and will be available in May.
EDIT 4: The SHIELD will come with GRID game-streaming service. 1080p, 60fps.
CONCLUSION: