I'll go first: I wish there was an app that can list the souvenirs that are actually made in the country you are in- I'd like to 'shop locally' while I'm travelling globally whenever I can. I call it the 'Souvenir Hunter' - somebody make it please!
I'd like a really good spreadsheet template for laying out a road trip that would figure distance, driving times, cost of gas; record info. about hotels/camp grounds, activities, sites to see, etc. It should also mesh with a mapping software such as Google Maps. There is a very good one on Google forms but is is so out-of-date that it no longer works. Apparently has not been updated to keep up with changes since 2009.
The closest thing I have ever found is Microsoft Streets & Trips but that software is no longer available. It even had GPS built in.
Oooh, this is a good question, here is my wishlist:
1. Tripit for Trip Planning - I love how once I've gone to all to the effort of booking each part of my trip, Tripit turns that into an itinerary of flights/hotels/activities/etc. What I'd love is a way to have a tool build potential itineraries for me, and then let me choose one (or parts of many) of them. Trip Planning & Itinerary creation have been tried dozens of times, but never well enough. I envision something which pulls in data from yelp/foursquare/booking.com/etc. And is able to create bespoke trips based on my input.
2. A truly global Data-SIM - I use a Truphone SIM when I travel overseas for work, and this works okay, except for in all of the places when I've really needed a good internet connection to be productive (UAE, China, etc.) Switching out SIMs, renting wifi devices, etc. Is a real pain-point in travel which I wish someone would fix.
3. The Opposite of an events calendar - I like to go to places when there aren't other people there. It's very easy to find out when a destination is going to be busy (event calendars, etc.), but it's hard to find out when I can go somewhere and it not be over-run with tourists.
4. A small plug - I wanted an app to help me find last minute hotels all over the world, so I built it: Booking Now