It is called Sun Guard. http://www.sunguardsunprotection.com/
Here is a copy of the hype;
Applying sunscreen and covering up with a T-shirt may seem like complete sun protection, but did you know you're not really shielding yourself from the damaging rays of the sun? Well, protecting the entire family from the sun's harmful UV rays has just become easier. By simply adding SunGuard to your laundry, you can transform everyday clothing into sun protective gear with a UPF protection of 30.
SunGuard works by washing an invisible shield into clothing that helps block more than 96% of the sun's harmful rays from reaching your skin. With the active ingredient TINOSORB® FD, a UV protectant from Ciba Specialty Chemicals, SunGuard can boost the UPF protection of a white cotton T-shirt from UPF 5 to UPF 30.
And, SunGuard is so easy to use! Add one package of SunGuard to a warm or hot water laundry load along with laundry detergent and you wash in skin protection for up to 20 washings. SunGuard won't change the color or comfort of clothing and is safe for even the most sensitive skin.
SunGuard has been featured on Good Morning America and The Today Show and is endorsed by leading dermatologists. SunGuard also has received the Good Housekeeping Seal of Approval as well as the Skin Cancer Foundation's Seal of Recommendation.