What You doing to me
The question was who sings the song, not who wrote it.
"The 2013 Toyota Prius: "Those Who Get It, Get It" with Raphael Saadiq" This commercial features a man with glasses (artist, Raphael Saadiq) singing a song with a guitar. He starts out singing from the open hatch of the car. He then gets up and starts singing to three woman who are in the back seat." http://www.popisms.com/TelevisionCommercial/67180/Toyota-Commercial-for-Toyota-Prius-2012-pr.aspx
the original song is by the bellamy brothers, called "let your love flow." petra Hayden sings it in the commericial.
The original track was written by copywriter Ted Kapusta.
Here's your answer as to "who sings the new Toyota Prius "Hum" song, "A Prius for everyone." - It is Petra Haden. For more information, please refer to the related link.
Come Along sung by Fabienne Deisol from her album "Between You and Me". MP3 available at Amazon
The Toyota song in the company's commercial is Wheel by Fisher.