While splitpipe is a useful program already, much more is in the works!
The data format (splitpipe(5)) and buffer of splitpipe have been built such that it is possible to restart failed volumes, provided they fail early enough.
This would allow the operated to continue a backup after, for example, inserting a used DVD instead of an empty one.
Larry McVoy has provided me with a program he wrote (Thanks!), but never released, that supports redundant backups, made in parallel to multiple tapes. It is a lot like splitpipe in fact, except that it writes to tape and not to arbitrary programs.
The redundant algorithm is interesting and might be implemented in splitpipe, but it would only be helpful to those with mutiple output devices.
Sequential output and input with multiple devices
If you have multiple readers or writers, you could make backups less user intensive. To start a restore, for example, place volumes one and two in your two drives, and start joinpipe.
Once a volume is done, joinpipe could then run a program to eject that volume. The operator could then every once in a while walk by and on seeing an ejected volume, insert the next one.
This would save a lot of waiting by the console.
The same could be done on making backups.