Can I install third-party apps on the Apple Watch?
Yes, just like iOS devices the Apple Watch will ship with pre-installed stock apps, and users will have the ability to download third-party apps from the Apple Watch Store. Here's a list of third-party apps that will be available when the Apple Watch begins shipping on April 24, 2015. You can see a list of other announced Apple Watch apps here.
Target
SPG
American Airlines
Nike+ Running
Instagram
MLB.com At Bat
BMW i Remote
Twitter
Citymapper
OpenTable
Evernote
TripAdvisor
NPR One
CNN
Honeywell Lyric
Green Kitchen
The Whole Pantry
Strava
Sky Guide
eBay
Redfin
PayByPhone Parking
Salesforce
Procreate Pocket
Dark Sky
Shazam
NYTimes
Mayo Clinic Synthesis
Invoice2go
Lutron Caséta
Rules!
PlayKids
Fandango
Citi Mobile
Expedia
Pacemaker DJ
Lifesum
Runtastic
Babbel
AMPLIFi Remote
BoxPop
CommitTo3
Mint Personal Finance
ESPN