BoatTender Sentinel Core
Your Boat's Brain - Monitor Anywhere, Anytime
Marine monitoring that bridges analog sensors and NMEA 2000 networks. Works standalone or optionally cloud-connected. Professional monitoring at a price that makes sense.
NMEA 2000 Certified • Works Without Cloud • Open Platform
Choose Your Connectivity
All Sentinel units work standalone via WiFi. Pick optional cloud connectivity that matches your cruising style - or use none at all.
Sentinel Core
WiFi Connectivity
Best For:
Marina and coastal cruising with WiFi access. Local monitoring on your boat's network.
Sentinel Coastal
LTE Connectivity
Best For:
Coastal cruising with cellular coverage. Monitor your boat from anywhere with internet.
Sentinel Offshore
Iridium Satellite
Best For:
Bluewater cruisers and offshore passages. Stay connected beyond cellular range.
What Makes Sentinel Different
Features competitors don't offer
WiFi Configuration
No PC Required
Set up from your phone using any browser. No Windows PC, no USB drivers, no complicated software.
Optional Cloud Monitoring
Your Choice
Optionally connect to check systems from anywhere. Works great offline too - cloud is completely optional.
Test Mode Built-In
Verify Before Launch
380 Hz test output validates RPM inputs without running the engine. No competitor has this.
What Can You Monitor?
Concrete examples of what Sentinel adds to your boat
Old Engines Without Digital Monitoring
Connect your 1980s Yanmar or Volvo to NMEA 2000. Wire up the analog oil pressure sender and temp sender you already have. Add a W terminal RPM pickup. Now your old engine appears on your chartplotter like it was built yesterday.
What you get: RPM, coolant temp, oil pressure on your MFD and phone
Add Tank Monitoring
Connect your existing fuel and water tank senders (most use 240-33Ω resistance senders). Sentinel has built-in calibration for common sender types or create a custom 3-point curve. See tank levels on your chartplotter and get low fuel alerts on your phone.
What you get: Fuel, water, black water, gray water levels anywhere
Bilge Pump Monitoring & Cycle Counting
Wire a digital input to your bilge pump float switch. Get a phone alert every time the bilge pump runs. Sentinel counts pump cycles—if it suddenly runs 20 times instead of twice a day, you know you have a leak before it becomes a disaster.
What you get: Instant bilge alerts + cycle history to catch problems early
Monitor Any Switch or Alarm
Digital inputs work with any switch: high water alarm, engine overheat, shore power connected, anchor windlass breaker, genset running. Get instant notifications and see status on NMEA 2000 displays. No programming required—just wire it and name it.
What you get: Any switch becomes a smart monitored alarm
All Together: Complete Engine + Tank + Alarm Monitoring
One Sentinel Core handles: engine RPM + coolant temp + oil pressure + fuel tank + water tank + bilge alarm + shore power status. Everything shows on your MFD and phone. Everything logs to the cloud. Install it once, monitor it forever.
Most popular: 4 analog inputs + 4 digital inputs = comprehensive boat monitoring
Can't find your exact use case?
With 4 configurable analog inputs and 4 digital inputs, Sentinel adapts to almost any sensor or switch. Temperature probes, pressure senders, flow meters, RPM pickups, and any 12V/24V switch all work. If you can wire it, Sentinel can monitor it.
Be First to Know
Join the waitlist to get early bird pricing and updates on Sentinel Core's launch.
Early bird pricing available • Q1 2026 Release • NMEA 2000 Certified