Something XBMC or Plex based are the closest naturally, there is an auto scrape add-on for XBMC and a pretty close Boxee skin available for it that re-creates the Boxee experience. However at the moment things are in a bit of a transition so you don't want to get something just yet.
Pivos XIOS was first generation XBMC set top box either running on top of stock Android 4.0 or a custom XBMC only firmware, not bad a little rough round the edges but it's due to be replaced by a newer model from Pivos by the end of the year, the XIOS also spawned a ton of clones which are worth ignoring.
Google are phasing out their old smart TV set top box platform (GoogleTV) and replacing it with a new Android TV platform based off Android 4.2. Hopefully this means new hardware in the pipeline that can handle XBMC and will also do a better job with Plex too.
For example you want an Android TV box for media decoding to have
* Fast enough hardware to run XBMC.
* To support running XBMC full screen (must be built into Android ROM otherwise you will see Android task-bar, this shouldn't apply to boxes running Android TV platform).
* To have licenses for Dolby/DTS bit-streaming in Android.
* Capable hardware decoders.
* SD card slot for storage so XBMC can save all metadata and coverart to it.
At the moment Pivos are the only one to take most of those into account so it's worth waiting to see what they come up with first before jumping on anything else. There are other stock Android devices out there but they often miss one or more of that checklist, on top of that with Android TV now official products based off that are likely in the works for example LG demoed various boxes some including TV tuners.
So essentially keep an eye on Pivos forums and see what's cooking.
Something non-XBMC, a Popcornhour A400 might do though the UI wont be as slick and it still is slightly manual I think like XBMC you tell it to scan for updates but the scanning is automated after that.