BerryVibe grew out of a request from a user for a tone to confim call hang-up. Speaker tones don't seem to work in call state, but vibrations do and they're less noticeable to who's around you.
BerryVibe makes brief vibrations when calls connect and/or disconnect, including regular and conference calls when people join or leave the call. Vibrations can be anywhere from barely more than a tap to a stronger pulse you can feel in your pocket if the phone calls someone accidentally.
http://store.berryreview.com/product.asp?id=37662&n=BerryVibe
Jam is a 25-function combination of BerryVibe plus 3 other apps which are often being purchased by the same people, and are now also offered together at a 30-40% discount. These are all solid apps that are either useful or fun and worth the money, but are buried under more-established apps and may benefit from joining forces at a competitive price.
http://store.berryreview.com/product.asp?id=37715&n=Jam
Jam includes lights, meters, and the BerryVibe 1.1 notifications. Its modules include 
Meters 1.1, 
BestFLASH+ 1.1.1, and 
RollerFlash 1.0.
At least right now, in the BerryReview Store you can get 
"I Charge Cool" 1.2 along with Jam for just 3 cents more. This deal is planned to be in effect at least until the 27th.