The following was posted to Essential's official Twitter account last night:

Name:  gem01.jpg
Views: 39
Size:  37.5 KB

"We've been working on a new device to reframe your perspective on mobile. It's now in early testing with our team outside the lab. Look forward to sharing more in the near future! #ProjectGEM"
Name:  gem02.jpg
Views: 35
Size:  36.8 KB

Additional photos were tweeted by Andy Rubin himself:

Name:  gem03.jpg
Views: 37
Size:  56.7 KB

Name:  gem04.jpg
Views: 34
Size:  89.7 KB

This new device seems to have caught the Internet off-guard; all that's been leaked prior to this are a few snippets of code on XDA. There is, however, plenty of speculation at the referring links below.

via Android Police, The Verge