In general the Unleashed’09 can be paired with any Bluetooth® enabled GPS receiver. The choice always depends on the purpose you want to use it for (rough weather conditions, fast moving objects etc.). We have made good experiences with Bad Elf GPS receivers and are currently selling the Bad Elf GPS Pro and Bad Elf GPS Pro+. Both are excellent GPS receivers that have a back-lit screen, logging, great battery life, and are MFI licensed (iOS compatible!). The Pro+ additionally uses Glonass and has a barometric altitude sensor.