Two suggestions that are valuable additions to any player's gig bag:

Electronic tuner: Take your pick of many under $40, but if your bassist plays a five-string, make sure the tuner can handle a low B -- some can't.
Recommended: Korg GA-1 or GA 30 Guitar/Bass Around $20
If you have more money to spend and want a tuner that can be used onstage, consider the Boss TU-2 Chromatic Tuner and power supply. This tuner has a pedal that takes your signal offline for silent tuning via LEDs. It has the added benefit of acting as power supply for Boss effects. Street cost is about $100.

PlanetWaves Bass ProWinder peg winder: Makes changing strings easy. The winder accommodates "elephant ear" tuning pegs and includes a wire cutter for snipping off excess string length. Less than $10

I use the Korg GA-30, and it works well, For stage use, the Korg "Pitch Black" Pedal Tuner is awesome for around 90 bucks...gotta love the true 100% pass through and the ability to power additional pedals on your pedal board when used with the optional AC adapter. It is totally transparent and easy to see on a dark stage,or even a brightly lit one, plus it's really accurate! Less wires around is always a plus.

Another great stocking stuffer I like is the C Tech Pocket Rock-It S1b Bass Headphone amp. Powered by a 9 volt battery. It has a swivel jack that plugs into your bass, an input for an mp3 player, and adjustable tones so you can jam privately anywhere without an amp. It includes a headset (which needs an upgrade) but for about 40 bucks, it does a great job of allowing you to practice anywhere you can't use an amp. Full review on this nifty item to follow tomorrow.....