What are some alternatives?
When comparing Agile Domain Search and Domainz.io, you can also consider the following products
Short Domain Search - Find short, available single-word domain names
Nuage - Nuage provides domain naming services.
Domainr - Domainr
Undeveloped - Domains you never thought were available
Lean Domain Search - Find a Great Domain Name w/ twitter handle availability
DomainWatch - Domain Monitoring Made Easy