The Proximo system can track up to four tags at the same time, each with its own customized name, icon, and sound effect; additional tags are sold for $25 each. Kensington expects that you’ll carry the fob around, and should you leave your iPhone behind, the fob will sound an alert; similarly, the iPhone can set off alerts on the fob or tags when you need to find them or if you move out of a designated range. Should you lose something, the app…