This app just released an update and it is awesome!
From the website:
March 30th 2010: Version 1.7 Finally Available
Thanks for your patience - it has been a while since the last update. This version finally adds waypoints, expands the search database to more than a million features, and updates the operation and display of the GPS.
I hope you enjoy the many new features in this version. Do review the user guide to make sure you don't miss anything. Feedback about the new features would be much appreciated - it's likely that things will be refined in future updates.
Here is a refresher of the main features [the ones in BOLD are very promissing:
Main Features
Topo Maps is a viewer for topographical maps published by the US Geological Survey and Natural Resources Canada. These maps cover the entire of the United States and Canada, including Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands. Their main use is for hiking and other outdoor activities.
In total, more than 70,000 individual maps are available. You can download as many of these as you like, limited only by the storage capacity of your iPhone or iPod. Downloads are free of charge.
Once downloaded, the maps are stored until you remove them. So unlike the iPhone's built-in Maps app, you can use Topo Maps when you have no network connection. Just download the maps that you need while you have WiFi or cellular coverage and you're all set.
As well as the maps themselves, Topo Maps also downloads terrain data. This is used to apply a 3D shading effect over the map to make the shape of the land clearer. You can even adjust the direction of the simulated sunlight that this effect uses. The terrain data is also put to other purposes, including a visibility mode which caclulates what should be visible from any viewpoint.
The app contains a database of more than a million placenames, which you can search to find the map that you need and to find individual features on those maps.
You can add your own waypoints to the maps, and download waypoint files from the internet.
You can use the iPhone's GPS to show your current position, and keep the map centered on your position as you move.
Updated your app! I really really want to see if they make this available to use the full capabilities of the iPad. If they added "tracks" what more would you need?