I didn't have to look further. Key Cafe has proved to be a reliable resource for key distrubution. STRONG RECOMMENDATION however - have your keys in more than 1 key cafe location. One of the locations I chose went offline for more than a month! And Key Cafe, as good as they are, are dependent upon local management. I was lucky, because the keys were checked out at the time. If they had been checked IN, they would have been unavailable for a month, which would have been a serious matter.
Key Cafe is economical and easy. However, to work properly, you must establish an excellent communication standard with all of your guests. And never use Instant Book or Quick Book in tandem with Key Cafe, or whatever it is called - bad idea if you want to maintain security.