Roland's flagship model for MIDI effect and sound, the VG99, allows for complete integration with three core processors. Dual modeling now allows the player to layer, combine and switch between amp models for guitar as well as bass. Modeled guitar and amplifier paths can be used at the same time. In addition, this MIDI technology is supported by any equipment baring USB or MIDI reception equipment so there's no need to purchase proprietary pickups or other reception devices; use what's already on hand. This effects board has it all, but is towards the higher end of the market.
A more modest version of Roland's MIDI system, the GR-20 offers similar MIDI effects for half the price. Use of this system requires no installation of a permanent MIDI pickup as with other MIDI effects processors. Simply attach Roland's included GK-3 divided pickup to the electric guitar in question, then choose the desired sound along with variation, and the board will do the rest. The breadth of effect and amp modeling is more limited than with more higher end models, but for affordability and function the GR-20 makes an ideal purchase.
For the musician seeking dirt cheap MIDI tone and modeling, look no further than Line6. Its widely popular POD line of guitar effects has branched into the realm of MIDI synthesizers, which is fortunate for the musician on a budget. Very affordable, the POD Floor Plus offers 32 classic and modern amp models with a host of effects able to be integrated into the guitar's sound. No special equipment or MIDI pickup system is needed for the POD as it plugs from the amplifier to the guitar as any effects pedal would.