Pandora Radio, the site that suggests music you might like based on your current tastes, has unveiled a prototype device that uses Wi-Fi to take Pandora content on the go. Pandora has also partnered with Sprint to offer the company's personalized streaming radio to Sprint mobile phone users. The service will be free for the first 30 days and costs $2.99 per month after that for users on a Sprint data plan. It looks like it will only work on five Sprint phone models at first, but it's set to work on all Sprint models by the end of June.