"Any" effect that can be put into a spell can be put into an item/wand. So, since sympathetic connections can be put into a spell, yes.
As for the second question(s)... (I'll assume the bones in the staff are "human")... first "why?"...o You can make the device hold concentration. This is handy for, say, a "Hold Person" type spell, which bones would lend themselves to easily. Other effects are possible.
o Environmental Triggers- the staff could work "automatically", if a trigger could be worked in there. Notify you of changes in Aura (Divine/Infernal Auras?), or when sunrise approached, etc. Perhaps casting a protective ward against spirits every night, regardless of your necromancer's mental state, whatever.
o Reach- if you can think of some spell with a range of "reach", but you'd rather not actually touch the target with your hand, but with your staff, here's your opportunity.
o Silent, No Gestures, etc - Depending what your "trigger" is, the usual headaches of those limitations (see p. 83) are not a consideration. That includes when restrained, or silenced. (I can think of more than one effect that a mage might want to cast silently and/or still, or when that first unfriendly hand grapples them.)
o No Fatigue, ever- Having a spell that you can cast infinitely without any chance of fatigue can be a lifesaver, especially in negative Aura areas (cities, graveyards, et al), or during longer combats. Having one or two reliable, versatile damage spells in an item makes a tired mage a reliable combat element, instead of a scared rabbit.
o Form/Effect Bonus. Getting a small benefit to creating the spell/instilling the effect allows for creating a larger final product, or the same effect faster. While some effects as spells are handier, for all the above reasons some are not.
Bodily pain, control, breaking, knowledge of health (who's alive, who's dead, who's hurt), protective/defensive spells cast on the necromancer himself, knowledge of bones underground, knowledge of the past history of bones, destruction of corpses ("Corpse to Dust" is very handy for cleanup of certain indiscretions and labwork), connections with spirits (anything that once had such bones), etc etc.
That's all that jumps immediately to mind, sorry.