HouseTrip is a service similar to Airbnb that puts holiday homeowners in contact with people looking for a short-term rental. The new iOS app includes a messaging tool so you can speak to the homeowner, alerts you to attractions in the area, and helps you to plan your itinerary.
The app uses Foursquare to make suggestions about places to visit while on holidays -- great if you need to find somewhere to eat or the nearest cafe. The HouseTrip app also includes an itinerary planning tool so you can schedule when you want to do what while you're away.
Hopefully, your trip will be problem-free, but there is a chance you might want to ask the homeowner a question -- perhaps asking for recommendations for shops. There is a built-in messaging system that you can use to talk with your host.
The app is currently available for iOS, but there is an Android version on the cards as well.