If it comes down between a PC and a
UDM I'd go with the UDM. Here is a thread where you can get one for $99:
Used - Like New UDM's for sale! - DetailingForums.com
He can also put together a pad package for you and he's a great vendor.
The
Flex would be another option, but the entry price is going to be higher.
EDIT: It seems like the $99 UDM's are all gone.