Since this is the first result for the "flask-security secure admin" google search, and there is no out-of-the-box solution yet, I think I can contribute. 
A similiar question was asked on the flask-admin project Issue List and a simple example using flask-login and mogodb is provided here.  
I made an example using SQLAchemy for a sqlite database and flask-security. See the sample flask app below:
 #!/usr/bin/env python
# -*- coding: utf-8 -*-
import os
import os.path as op
from flask import Flask, render_template, url_for, request
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.event import listens_for
from flask.ext.security import current_user, login_required, RoleMixin, Security, SQLAlchemyUserDatastore, UserMixin
from flask_admin import Admin, AdminIndexView
from flask_admin.contrib import sqla
# Create application
app = Flask(__name__)
# Create dummy secrety key so we can use sessions
app.config['SECRET_KEY'] = '123456790'
# Create in-memory database
app.config['DATABASE_FILE'] = 'sample_db.sqlite'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + app.config['DATABASE_FILE']
app.config['SQLALCHEMY_ECHO'] = True
db = SQLAlchemy(app)
# Create directory for file fields to use
file_path = op.join(op.dirname(__file__), 'static/files')
# flask-security models
roles_users = db.Table('roles_users',
        db.Column('user_id', db.Integer(), db.ForeignKey('user.id')),
        db.Column('role_id', db.Integer(), db.ForeignKey('role.id')))
class Role(db.Model, RoleMixin):
    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column(db.String(80), unique=True)
    description = db.Column(db.String(255))
class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))
    active = db.Column(db.Boolean())
    confirmed_at = db.Column(db.DateTime())
    roles = db.relationship('Role', secondary=roles_users,
                            backref=db.backref('users', lazy='dynamic'))
# Create Security
user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security(app, user_datastore)
# Only needed on first execution to create first user
#@app.before_first_request
#def create_user():
#    db.create_all()
#    user_datastore.create_user(email='yourmail@mail.com', password='pass')
#    db.session.commit()
class AnyModel(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Unicode(64))
    def __unicode__(self):
        return self.name
class MyAdminIndexView(AdminIndexView):
    def is_accessible(self):
        return current_user.is_authenticated() # This does the trick rendering the view only if the user is authenticated
# Create admin. In this block you pass your custom admin index view to your admin area 
admin = Admin(app, 'Admin Area', template_mode='bootstrap3', index_view=MyAdminIndexView())
# Add views
admin.add_view(sqla.ModelView(AnyModel, db.session)) 
# To acess the logout just type the route /logout on browser. That redirects you to the index
@login_required
@app.route('/login')
def login():
    return redirect('/admin')
@app.route('/')
def index():
    return render_template('index.html')
if __name__ == '__main__':
    # Build sample db on the fly, if one does not exist yet.
    db.create_all() 
    app.run(debug=True)
Please refer to the flask-security docs to learn how to customize the login page.
Hope this helps.