Right okay so here's a question I'm hoping someone can provide clarity to under the D&D 3.5 rule set. I've used the PHB, DMG and the 3.0 Rules of the Game Animals Part 4 to research an answer though I'm no closer to a solution.
From the ranger or druid class ability animal companion, spells can be shared with the companion via the share spells ability. This is also true of magic items, from Rules of the Game Animals Part 4:
You and your animal companion can share effects from magic items only if the effect is a spell that you can target on yourself. For example, you and your animal companion can share a barkskin spell cast from a wand, but cannot share the armor bonus from bracers of armor.
How does this apply to magic items with continuous ongoing effects? Say for example the character is wearing a Mantle of Spell Resistance granting the wearer spell resistance 21, the wearer approaches and stays within 5ft of his animal companion choosing to share his spells with the animal companion. Does the animal companion also receive spell resistance 21 provided the wearer stays within 5ft of his animal companion?
Or is the understanding that sharing spells is only applicable if the character casts a spell or produces some effect at the time or after the character approaches and remains within 5ft. For example the character is riding along on his animal companion heavy horse suddenly the ground beneath them gives and both the animal companion and the character plunge down a 30ft pit. But luckily the character is wearing a ring of feather falling and therefore the feather fall spell is activated and BOTH the character and the animal companion drift slowly and safely to the bottom?
Last example using the character and heavy horse animal companion again from above, the character and animal companion are riding along the trail when suddenly an orc shaman jumps out of the bushes and casts magic missile, the character is wearing a brooch of shielding which protects against magic missile however the orc shaman casts the spell at the horse. Does the shield spell effect of the brooch of shielding protect the horse?
All of the above examples use reactive spells or effects, the character hasn't actively cast a spell or produced an effect to share.
Hoping someone can shed some light on this.