I teach 5th grade band and at this level there is really no reason to invest in a set of Chimes or a Vibraphone.  Still, on rare occasions I program music into the concerts that might require such instruments, and rather than leaving them out or having the kids play them on their bell set I have long wished for a good, low cost alternative.  I may have found one in the PercussionSS iPad app.
PercussionSS is a collection of six different virtual percussion instruments.  The set includes the vibraphone, xylophone, marimba, glockenspiel, tubular chimes, and wind chimes.  Simply select the appropriate instrument and a scaled down visual representation of the keyboard appears on the screen.  Sadly the images are not scalable so the marimba and xylophone bars are kind of small, but for younger kids they are just fine.  

There is also a second app by the same author called PercussionSS2 that includes a set of Crotales, Kalimba, Lithophone, Agogo Bells, Metal Plates, and Water Glasses.  All of the instruments in both apps are also available as individual downloads for around $2 each.  Other similar virtual instrument apps including steel drums and others are available from the same maker through in-app purchases using special, free versions of the app.  

The main reason I was searching for this kind of app was for the tubular chimes.  We borrowed a set one time to play a piece at a concert but the student was so short we had to have him stand on a milk crate in order to play them properly.  Plus, he was unable to practice with the real instrument until the day of the concert.  With this app a student can at least practice their parts and if you route the sound through a PA system the band can at least hear what the part will sound like on the day of the concert.

Is PercussionSS an idea solution for this kind of situation?  Maybe not, but the sounds are very clean and sound quite realistic, good enough for a rehearsal or in a pinch when something goes wrong.  Plus, spending $14 on an app versus spending $7500 on a set of chimes that might be used once a year is a very good investment in my opinion.  Take a look at the PercussionSS app on the Apple App Store and see what you think.