What is this tall purple plant?

Mystery plant (copyright Jaipi Sixbear 2014)

Let's take a break from weeding the garden to play name that plant.

Does anyone know what this tall purple plant might be? The plant was growing in the back yard of my partner's customer. (He's a plumber) She says it's a weed. Is it? I know there's an app that you can use to help with this kind of thing.

Does anyone have a plant identification app?

Supposedly, you can upload a picture and it will identify the plant. So, here's some pictures of this unusually tall, colorful flowering purple plant. I'm not worried about anyone using the pics. We just took them to see if anyone could identify the plant.

Note: This post was originally published on my old blog of the same name on a different site. I've since found out what the plant is, but I'm not telling. It's more fun to guess, so I'm leaving this open for comments.

Feel free to leave a comment if you know what it is.