Inglett, who was signed only a month ago by the Rays, will likely fill the need of a left handed bench bat for the Astros. As R.J. Anderson notes, this trade is likely an agreement the team had worked out with Inglett, much like Adam Kennedy last season. If he did not make the major league roster, and another team had an offer for a big league job, the Rays would make the necessary accommodations.
There's no indication as to what the Rays will receive, but it likely won't be anything substantial. The Rays did Inglett a favor, and I hope he does well in his new role.