Adding a tail also involved adding an extra motor to the robot, but there was no way that the designers could tolerate such inefficiency. So, the tail motor and gear can team up with a gear on the jumping motor to give the robot the ability to move horizontally along the ground. My guess is that the next iteration of this robot that we see will (somehow) have that motor enablingthree abilities instead of just two.
The total weight of the robot is still just 26 grams, and it's only 7.5 centimeters tall. It can jump over 80 centimeters up (with a 75 degree takeoff angle), and while "running," it can reach speeds of nearly 4 cm/s. In addition, the robot is equipped with on-board sensors, and of course it can be controlled wirelessly or made fully autonomous, and the designers speculate that it might be appropriate for applications like search and rescue, military surveillance, and environmental monitoring.
Officially, this research will be presented at IROS 2013 in Toyko this November, but a pre-print edition of the full paper is already available online here.