Well, it wasn't too painful given that I've managed to convert map data intended for Ozi Explorer to Mappero-compatible format (I didn't think this is possible at all). Pre-downloaded google or yandex maps for that places didn't suit me. What disappointed me about mappero is that it was destroying recorded GPX tracks from time to time (seems like this bug is already fixed) and it seems to be leaking memory so if you leave it running for a long time everything tends to become very sluggish. Other than that, it was tolerable. As of custom-soldered cable, it's the only way to charge devices that support modern USB charge standard from older chargers that don't support it.