diff --git a/navpoint/gui.py b/navpoint/gui.py
index 4f3c428..7a1bd94 100755
--- a/navpoint/gui.py
+++ b/navpoint/gui.py
@@ -1,9 +1,48 @@
 import tkinter as tk
+from tkinter import ttk
 import pyqrcode
 import navpoint.fix_path
+import navpoint.usb
 
 
-def run(link):
+def choose_mode():
+    def _usb_clicked():
+        window.destroy()
+        global mode
+        mode = "usb"
+
+    def _mobile_clicked():
+        window.destroy()
+        global mode
+        mode = "mobile"
+
+    window = tk.Tk(className="navpoint")
+    window.title("Navpoint")
+    window.resizable(width=False, height=False)
+
+    global mode
+    mode = ""
+
+    ttk.Label(window, text="How should Navpoint obtain location data?").pack()
+    usb_button = ttk.Button(
+        window, text="USB GPS receiver (NMEA)", command=_usb_clicked
+    )
+    usb_button.pack()
+    mobile_button = ttk.Button(
+        window, text="Phone running Navpoint Mobile", command=_mobile_clicked
+    )
+    mobile_button.pack()
+
+    try:
+        window.iconbitmap(navpoint.fix_path.fix_path("icon.ico"))
+    except tk.TclError:
+        pass
+
+    window.mainloop()
+    return mode
+
+
+def show_qr(link):
     window = tk.Tk(className="navpoint")
     window.title("Navpoint")
     window.resizable(width=False, height=False)
diff --git a/navpoint/run.py b/navpoint/run.py
index 3355443..f67672a 100755
--- a/navpoint/run.py
+++ b/navpoint/run.py
@@ -1,9 +1,15 @@
 import navpoint.local_server
 import navpoint.phone_server
+import navpoint.usb
 import navpoint.gui
 
 
 def run():
-    navpoint.local_server.run()
-    link = navpoint.phone_server.run()
-    navpoint.gui.run(link)
+    mode = navpoint.gui.choose_mode()
+    if mode == "mobile":
+        navpoint.local_server.run()
+        link = navpoint.phone_server.run()
+        navpoint.gui.show_qr(link)
+    elif mode == "usb":
+        navpoint.local_server.run()
+        navpoint.usb.run_ui()
diff --git a/navpoint/usb.py b/navpoint/usb.py
new file mode 100644
index 0000000..8e0bb24
--- /dev/null
+++ b/navpoint/usb.py
@@ -0,0 +1,140 @@
+import threading
+import queue
+import tkinter as tk
+from tkinter import ttk
+from tkinter import messagebox
+from serial import Serial
+from pynmeagps import NMEAReader
+import serial.tools.list_ports
+import serial.serialutil
+import navpoint.content
+import navpoint.fix_path
+
+
+def main(port, window, updates):
+    try:
+        with Serial(port, timeout=3) as stream:
+            reader = NMEAReader(stream)
+            updates.put(
+                (
+                    "Connected",
+                    port,
+                )
+            )
+            window.event_generate("<<newData>>", when="tail", state=1)
+
+            while True:
+                _, parsed_data = reader.read()
+                try:
+                    lat = parsed_data.lat
+                    lon = parsed_data.lon
+                    time = parsed_data.time
+                    date = parsed_data.date
+                    navpoint.content.content = f"""<?xml version='1.0' encoding='us-ascii'?><kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2"><Document><Style id="icon"><IconStyle><Icon><href>http://127.0.0.1:8888/marker.png</href></Icon></IconStyle></Style><name>Navpoint</name><open>1</open><Placemark><name>Position</name><styleUrl>#icon</styleUrl><Point><coordinates>{lon},{lat},0</coordinates></Point><description>{date} {time} UTC</description></Placemark></Document></kml>"""
+                    updates.put(
+                        (
+                            "LocationUpdate",
+                            {
+                                "lat": lat,
+                                "lon": lon,
+                                "time": f"{date} {time} UTC",
+                            },
+                        )
+                    )
+                    window.event_generate("<<newData>>", when="tail", state=1)
+
+                except AttributeError:
+                    pass
+    except serial.serialutil.SerialException as e:
+        updates.put(
+            (
+                "Disconnected",
+                port,
+            )
+        )
+        window.event_generate("<<newData>>", when="tail", state=1)
+        messagebox.showerror(
+            "Navpoint Error", f"Error reading from port {port}: {str(e)}"
+        )
+
+
+def run(port, window, updates):
+    threading.Thread(
+        target=main, args=(port, window, updates), daemon=True
+    ).start()
+
+
+def clear(queue_to_clear):
+    try:
+        while True:
+            queue_to_clear.get(block=False)
+    except queue.Empty:
+        pass
+
+
+def update_dropdown(dropdown):
+    dropdown["values"] = ["[Select port]"] + [
+        f"{port.device} ({port.description})"
+        for port in serial.tools.list_ports.comports()
+    ]
+    dropdown.current(newindex=0)
+
+
+def run_ui():
+    def selected(event):
+        selection = dropdown.get().split()[0]
+        if not selection.startswith("["):
+            clear(updates)
+            run(selection, window, updates)
+
+    def new_data(event):
+        try:
+            purpose, content = updates.get(block=False)
+        except queue.Empty:
+            return
+
+        if purpose == "LocationUpdate":
+            updated.config(text="Last updated: " + content["time"])
+        elif purpose == "Connected":
+            status.config(text="Connected to " + content)
+            dropdown.pack_forget()
+            refresh.pack_forget()
+        elif purpose == "Disconnected":
+            status.config(text="Not connected")
+            update_dropdown(dropdown)
+            dropdown.pack()
+            refresh.pack()
+
+    def refresh_clicked():
+        update_dropdown(dropdown)
+
+    window = tk.Tk(className="navpoint")
+    window.title("Navpoint")
+    window.resizable(width=False, height=False)
+
+    status = ttk.Label(window, text="Not connected")
+    status.pack()
+
+    updated = ttk.Label(window, text="Waiting for location")
+    updated.pack()
+
+    n = tk.StringVar()
+    dropdown = ttk.Combobox(window, state="readonly", textvariable=n, width=40)
+    update_dropdown(dropdown)
+    dropdown.pack()
+
+    refresh = ttk.Button(
+        window, text="Refresh device list", command=refresh_clicked
+    )
+    refresh.pack()
+
+    dropdown.bind("<<ComboboxSelected>>", selected)
+    window.bind("<<newData>>", new_data)
+
+    updates = queue.Queue()
+    try:
+        window.iconbitmap(navpoint.fix_path.fix_path("icon.ico"))
+    except tk.TclError:
+        pass
+
+    window.mainloop()
diff --git a/requirements.txt b/requirements.txt
index adca132..33291f6 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,4 @@
 pyqrcode
 tornado
+pyserial
+pynmeagps