YotaPhone 2, the handset Amazon should have made, is coming to U.S.

An innovative Android phone with a power efficient e-ink touchscreen on the back would have played to Amazon's strength: Kindle reading.

One of the more innovative handsets to hit the market in a few years will go on sale in the U.S. this summer. And you won't mistake it for any other phone: The YotaPhone 2 has a standard display on the front that's paired with a high-resolution e-ink screen on the back.

Like all other devices that use e-ink technology, the secondary screen only draws power from the battery when the screen refreshes.

Think of the YotaPhone 2 as a combination between an Amazon Kindle and an LTE-capable Android smartphone. You get the traditional screen for typical phone activities and apps while the e-ink screen is ideal for more static information such as your agenda. That rear display is interactive though, thanks to capacitive touch support, just like the front screen.

Because the e-ink panel is fully integrated with the phone as a secondary display -- you can mirror the standard display on the back panel -- any Android app can theoretically be used on it.

You could quickly dismiss or respond to notifications on the back panel and use less power, for example. Or you could read a book, display a map or show a task management app on the more power efficient display. Keep in mind that e-ink displays can be slow to refresh. I wouldn't want to do anything that's graphically intensive on the back of this handset.

As a result of the second screen, the company behind the YotaPhone 2 says power consumption can be measured in days. Of course, it depends on how much you rely on the e-ink display compared to the 5-inch AMOLED panel on the phone's front face. The 2500 mAh battery will likely last only a day if you use the traditional front screen a majority of the time.

Since it doesn't have a carrier partner here in the U.S., the YotaPhone 2 will become available through direct sales in an Indiegogo campaign that begins May 19. Yota hasn't announced the price but it has reduced the cost in other markets. In the U.K., for example, the handset is now priced at £440.00 or US $680, down from £555.00.

It's a shame Amazon's Fire Phone wasn't more similar to the YotaPhone 2. The company has far more experience with e-ink devices than most and could have touted the versatility of the secondary display by putting its Kindle app front and center on such a phone.

Instead, it opted for multiple camera sensors, 3-D interfaces and a focus on purchasing items with ease. So far, that hasn't worked out too well for Amazon's Fire Phone.

See also: YotaPhone 2 review: Novel, but expensive, dual-screen smartphone