We'd like to do some pet dog tracking but are having a hard time finding a good tag. We used to use i-got-U's but they don't seem to be available. There are a ton of new pet dog trackers but they all seem to be networked, so they can charge you for the live data. We don't need live data, would like a unit to last a few weeks, ideally, then take it off, get the data, recharge the battery, and send it off on another dog. I've been looking around for other small GPS loggers that are less expensive than the fully-engineered widllife tags (which also usually don't have replacable batteries) without much luck. Anyone have any suggestions?