As far as microchips go, there is a great difference between the Home Again and AVID systems. AVID was originally developed for identifying zoo animals, and it is by far the most reliable system. I have been using AVID chips for at least eight years, and I have yet to see a "dud". Not so with Home Again. For those of you who have the Home Again chips, there is absolutely no problem with having an AVID chip implanted as well. That way you have the peace of mind that at least one of one them should be recognized by a scanner. There is to my knowledge one other major chip company, Humana, but I have yet to come across any pets with their ID.
Another tip: AVID makes tags that they give with the microchip numberto put on the collar. DO NOT put these on your dog!!! The chip number can be used not only as ID, but as proof of ownership as well...treat your dog's chip number like your social security number. No one should know it but you and your vet. Some people in the animal industry, sadly, do not request to see the chip certificate and will accept knowledge of the number as proof that someone is the dog's owner. We all know there more to it than that. AVID is especially good about safeguarding owner information and will not change chip information without signed permission from the original applicant. That brings me to another issue: make sure your chip info is updated regularly. I cannot tell you how many dogs I find that have chips registered to puppy mills, breeders, shelters, vets. Their owners never bothered to register the chips in their own names. Do not rely on others to track you down, make sure your info is up to date so your baby gets home fast!!