I like the idea of giving the sorcerer something that allows him use his spell slots for something other than his spells. One thing that I can think of is spells that form a logical spell chain, such as a Rod of Monster Summoning that can have the sorcerer cast Summon Monster I, SM II, SM III,... Summon Monster IV, as if he had all of these spells as part of his personal spell list. While holding the rod, he just uses a spell slot to cast the respective spell. A third level spell slot to cast Summon Monster III, for example. Of course, he's not able to cast a level of the spell that is higher than he can normally cast.
One thing that I would add to such an item is the metamagic ability to increase the duration to the next duration category if you cast one of these spells two levels higher than it is. So a Summon Monster I spell could last 1 minute/level as a 3rd level spell, 10 minutes/level as a 5th level spell, or 1 hour/level as a 7th level spell. So, you could have a low CR traps monkey walk in front of the party, trigger any pit traps, draw any ambush attacks, open doors, pick up items, etc. Or you can have creatures guard you while you camp.
I think that I would also have the rod grant to the wielder the ability to speak, understand, read, & write Celestial, Infernal, [Aquatic], Auran, Ignan, and Terran.