Hi! Based on my own experience, currently Google new Terms & Policy, they don not allow any linking to any webpage that you do not owned. If you would like to do so, most probably you will have to get permission first and inform Google on this permission before even publishing your apps as you know Google will suspend your apps without notice and just give a standard email saying your accounts is suspended due to their Terms & Condition.
You could also be an affiliates to hotel reservation website but unfortunate under the new Google Terms & conditions also, they put up an email saying something like this... " although Google acknowledge that affiliates links are legal but under their new Terms & Condition, they do not allow any affiliates link to third party website.
Anyway, if others have their own other experiences, please do share with us here. I was earning very good comission from one of the hotel affiliates I joined before, but my apps has been suspended by Google recently.