The online retailing giant Amazon is expected to unveil a smart phone at a media event in Seattle today, with tech observers buzzing over the anticipated bells-and-whistles-like 3D features.

But many think the phone will largely function as a handheld shopping cart that you can then fill with more of Amazon’s stuff.

“They want you to interact with them five, ten times a day, and the mobile phone is a great way to ensure that Amazon is there whenever you might need something,” says James McQuivey, a media analyst with Forrester Research.

McQuivey says an Amazon phone might also include a built-in payment system that could be used with any retailer.

Colin Gillis, senior technology analyst with the brokerage firm BGC Financial, thinks the phone might well be free. Same goes for the data if you’re, say, downloading music from Amazon.

“It’s the classic razor and blades. You can have the razor for free as long as you keep buying blades from us,” Gillis says.

Even so, Gillis thinks a smart phone won’t bust Amazon out of its low profit margins.