If you're in possession of a jailbroken iPhone, you don't have to rely on "unofficial" offline maps to get you to your destination when 3G of Wi-Fi isn't available.
I recently came back from a trip to NZ and for some reason, my phone refused to connect to Vodafone NZ, despite making sure roaming was active, both via my online account and talking directly to Vodafone support. So, I was left to find an alternative way to assure I'd have a map, no matter where I was. That, and I didn't want to pay roaming fees when I had good access to free Wi-Fi to download the data I needed beforehand.
Yes, the simple solution would have been to buy a directory or grab local maps from information and visitor centres. Which we did. But nothing quite beats the combo of Maps and GPS. That's where OfflineMaps steps in. Available on Cydia, this app lets you store cached Maps and routes and recall them at your leisure.
Going by the Google Code page, I was originally put off by the idea that I'd have to download maps, upload them to my phone and then load them into the Maps app. Turns out, you don't have to do that at all.
We've already mentioned how you can have "unofficial" offline maps by browsing the area and selecting the route before you go offline, but I've found this is a very fragile state to leave the Maps app in -- fire up the wrong combination of apps, switch off your phone or reboot the Springboard and you might find the cache cleared. I found firing up Cydia was enough to wipe it.
With OfflineMaps installed, you can browse the area and/or jump between the points in the route, cache them, and then store them away with a custom name using OfflineMaps. If the cache is cleared, you just re-import the cache data and open the Maps and, and you'll find it all restored.
The cached data isn't exactly small. Stored maps of the route between Beachlands and Auckland Airport came out to 22MB. Hardly massive, but big enough that keeping a record of every trip you make offline might become prohibitive.
If you were like me and thought there was some pain-staking process involved in using this Cydia app, don't worry, it's very straightforward.