From the maker of jgEffects and many more apps comes jgBassEffects, a multi-effects app just for bass players. The app itself is free, but has a bunch of in-app purchases. Those appear to be free at the moment, as well – but I’d check before you go buying anything it.

From the publisher:

Hi, bass players!
A multi-effects processor for electric bass guitar was born. Simply connect the electric base guitar to iPhone / iPad, you can enjoy unique sound effect like no other!

Compatible audio interfaces are Apogee JAM, iRig, iRigHD, TASCAM iXZ.
The app supports “Inter-App Audio” which works together with applications such as GarageBand.

“When it gets stuck with recording”, “When getting tired of the usual sound”, please try using fantastic jgBassEffects. It realizes low latency and real time output, and it corresponds to any electric bass guitar!

++ Effector Details ++
Up to three effectors can be used simultaneously.
We are planning to add a new effect.

+ Noize Gate +
Reduce noise.
Control: Sens, Press

+ B Fuzz +
Sweet tone but intense fuzz.
Control: Blend, Gain, Hunny, Color

+Bass Delay +
A standard delay is also available.
Control: Blend, Time, Feedback

+ Bass Reverb +
Simple reverb is also available.
Control: Strength

+ Ring Mix +
Overdrive, characterized by ring modulation.
Control: Blend, Gain, Tone

+ Auto Revolving Wah B +
Auto Rotation Filter Wah.
Control: Color, Speed, Q

+ Mod x Flanger +
Strong flanger by modulation.
Control: Blend, Depth, Range

+ Tremolrato B +
Tremolo + Vibrato + Panning effect.
Control: Time, Depth, Rate, Tremolo

++ Compatible device ++
It is recommended to use newer models than iPhone 5s and iPad mini 4.

Official Web:

jgBassEffects is on the App Store now and is free with IAPs.