Meet Alexa, the voice behind the interactive Amazon Echo speaker. Alexa is a voice controlled personal assistant. Unlike Apple's Siri, Microsoft's Cortana, and Google Now, it has a physical presence. It is 20 cm-tall black cylinder, which contains Wi-Fi, two speakers, seven microphones, and connects to the cloud.  Pringles-can-sized Echo costs around $200.

According to Mashable,  the device can already do a variety of things, including answer your questions, play music, control your smart home lights and provide updates on news, sports, weather and traffic.

Voice recognition isn't the challenge-that's the easy part now. The problem understands what we mean, the context of our requests. Virtual assistants today do not have effective memory," says Norman Winarsky, vice president of ventures at SRI and a co-creator of Siri, which SRI sold to Apple. Each time you talk with one, it's like you're meeting them for the first time, he says.

WSJ says that, spend a little more time with Alexa, and the dream of a virtual assistant in a bottle begins to fizzle. "Alexa, can you give me a recipe for chocolate chip cookies?" I asked. "Sorry, I didn't understand the question I heard," she said. "How long will it take to drive to the office?" She couldn't

Virtual assistants have taken a few baby steps in understanding context. You can now ask Siri, "Any good sushi places around here?" and she will use your location to make recommendations. Then if you change your mind and ask, "What about Mexican?" she remembers that you just asked about restaurants.'

Cortana helpfully asks for more information about the people and places that matter to you. You can tell Cortana to "remind me the next time my dad calls to tell him about the trip," and it will know which call to flag.

Amazon says Echo is open to outside developers, but Cortana can already control smart home systems like Insteon, and Siri will soon star as the master controller of Apple's HomeKit, which will connect to lots of different smart home devices.

Ultimately, what's holding back the Echo is that Alexa doesn't have access to my contacts, calendar and email, or where I spend my time.

What makes Alexa stands out from the rest is she isn't just a feature on a phone. She lives in your living room or kitchen, so everyone in the family can use her, hands-free. The Echo is always on and waiting for someone to call out, "Alexa." (If you live with a real Alexa, you can change the wake-up word to "Amazon.")

 Echo's website says the device "continually learns and adds more functionality over time."  Amazon's Echo only costs $100 for Amazon Prime members for a limited time. You can connect a phone, tablet or computer to the Echo via Bluetooth to play music from Pandora, iTunes or Spotify.

Amazon is just getting started with the Echo. But given the challenges, it's clear that Alexa has a ways to go to live up to her potential.